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php.ini

Introduction

Location

• Windows: usually located inC:\php\php.iniOr in the installation directory.
• Linux: Commonly found in/etc/php/version number/apache2/php.inior/etc/php/version/cli/php.ini。
• Availablephp --iniQuery the configuration file used by the CLI.

php.ini priorities used

1. If using-cIf the parameter is specified, the path will be loaded first.php.ini。
2. environmental variablesPHPRCthe specified directory.
3. The default installation directory when PHP is compiled (availablephp --iniorphpinfo()query).
4. In some operating systems, you may also look for/etc/php.iniorC:\Windows。

Common settings

; Set time zone
date.timezone = Asia/Taipei

; show error
display_errors = On
error_reporting = E_ALL

; Upload file size
upload_max_filesize = 20M
post_max_size = 25M

; Memory limit
memory_limit = 256M

; Maximum execution time (seconds)
max_execution_time = 30

Load settings

• Revisephp.iniAfterwards, you need to restart Apache, Nginx or PHP-FPM for it to take effect.
• availablephpinfo()Check the currently loadedphp.iniPath and parameter values.

Things to note

• Different execution environments (Apache, CLI, Nginx) may use differentphp.ini。
• Can be created.user.inior.htaccessOverwrite some settings.
• Modify the settings related to error output. It is recommended to turn it on in the development environment and turn it off in the official environment.

PHP boolean

The Boolean value is the simplest data type in PHP. It can only represent two states: **true** or **false**. Boolean values ​​are often used for control processes (e.g.if/elseconditional judgment) and logical operations.

Basic usage

You can use keywordstrueorfalseto define a Boolean variable. These keywords are not case-sensitive (for example,TRUE、Trueortrueare the same), but it is generally recommended to use lowercasetrueandfalseto comply with standard practice.

$is_active = true;
$is_logged_out = FALSE; // Although uppercase letters are possible, they are not recommended.

//Conditional judgment
if ($is_active) {
    echo "<p>The user is currently active.</p>";
} else {
    echo "<p>The user is currently inactive.</p>";
}

Boolean value conversion (Casting)

When PHP expects a Boolean value but is given another data type (e.g. inifcondition), PHP will automatically convert (or type cast) the value to a Boolean value.

The following values ​​are considered false (called Falsy values):

• Bollinger valuefalseitself.
• integer0(zero).
• floating point number0.0(zero).
• empty string""or''。
• String"0"(a string containing the single digit zero).
• empty arrayarray()or[]。
• special typeNULL。
• A SimpleXML object without any child nodes (uncommon).

All other values, including any non-zero number, any non-empty string (even"false"or" "[including spaces]), will be regarded as **true (true)** (called Truthy value).

Type conversion example

$a = 0;
$b = "Hello";
$c = "";
$d = [1, 2];
$e = null;

echo "<h3>Falsy value example</h3>";
if (!$a) { // $a (0) converts to false
    echo "<p>$a (integer 0) is treated as FALSE.</p>";
}
if (!$c) { // $c (empty string) converts to false
    echo "<p>$c (empty string) is treated as FALSE.</p>";
}
if (!$e) { // $e (NULL) converts to false
    echo "<p>NULL is treated as FALSE.</p>";
}

echo "<h3>Truthy value example</h3>";
if ($b) { // $b ("Hello") converts to true
    echo "<p>$b (non-empty string) is treated as TRUE.</p>";
}
if ($d) { // $d (non-empty array) converts to true
    echo "<p>Non-empty arrays are treated as TRUE.</p>";
}

Cast to boolean

You can also use(bool)orboolval()The function explicitly converts the variable to a Boolean value, which is useful when debugging or when strict type checking is required.

$f = "0"; // string of number zero
$g = 100; // positive integer

$f_bool = (bool)$f;
$g_bool = boolval($g);

echo "<p>The string '0' is converted to: ";
var_dump($f_bool); // Output: bool(false)
echo "</p>";

echo "<p>The integer 100 is converted to: ";
var_dump($g_bool); // Output: bool(true)
echo "</p>";

PHP comparison operators

In PHP, comparison operators are used to compare two values ​​(numbers or strings). According to the comparison result, it will be returnedtrueorfalse. Understanding the difference between "loose comparison" and "strict comparison" is the key to avoiding program bugs.

1. List of commonly used comparison operators

2. In-depth analysis: the difference between == and ===

This is the most common area of ​​confusion in PHP development. PHP is a weakly typed language.==Will try to convert variables of different types into the same type before comparing them, and===No conversion is performed at all.

loose comparison (==)

This is true as long as the "values" are equal after conversion:

$a = 100; // integer (int)
$b = "100"; // string (string)

if ($a == $b) {
    echo "Equal"; // This will be executed because PHP converts strings into numeric comparisons
}

Strict comparison (===)

The "value" must be exactly the same as the "data type":

$a = 100;
$b = "100";

if ($a === $b) {
    echo "Equal";
} else {
    echo "not equal"; // this will be executed because int is not equal to string
}

3. Special cases: ternary operator and merge operator

The shorthand syntax makes your code cleaner when dealing with comparison logic:

• Ternary operator (Ternary): $result = ($a > $b) ? "A Big" : "B Big";
• Null Coalescing: $name = $input_name ?? "Visitor";(Provides a default value when the variable does not exist or is null).

Safety advice:When performing authentication, permission checks, or API return value judgment, be sure to use===. For example checkstrpos()The return value of0(position) andfalse(not found) in==will be treated as the same, which will lead to logical errors.

PHP array

In PHP, an array is a very useful composite data type that can store multiple values ​​in a single variable. PHP's array is actually an ordered map. A map is a type that associates Values ​​with Keys.

Features of PHP Arrays

• Mixed keys:The keys of the array can be integers (Index, index) or strings (Key, key name).
• Mixed values:The values ​​in the array can be any PHP data type, including other arrays (forming multidimensional arrays).
• Dynamic size:The size of the array is dynamic and you do not need to declare its capacity in advance.

array type

PHP's arrays can be roughly divided into three common forms based on the type of their keys:

1. Indexed Arrays

Use consecutive integers as keys. If you don't specify a key when building the array, PHP will start with0Start automatically assigning integer indexes.

//Create an indexed array
$fruits = array("apple", "banana", "orange");
// Or use shorthand syntax (after PHP 5.4)
$colors = ["red", "green", "blue"];

//Access elements
echo $fruits[0]; // Output: apples
echo $colors[2]; // Output: blue

2. Associative Arrays

Use strings as keys (key names). This allows you to use meaningful names to access the values ​​in the array.

//Create an associative array
$person = array(
    "name" => "Xiao Ming",
    "age" => 25,
    "city" => "Taipei"
);

// Or use shorthand syntax
$scores = [
    "Math" => 90,
    "English" => 85
];

//Access elements
echo $person["name"]; // Output: Xiao Ming
echo $scores["English"]; // Output: 85

3. Multidimensional Arrays

The values ​​in the array are in turn another array. This is typically used to store tabular or hierarchical data.

$students = [
    [
        "name" => "Alice",
        "scores" => ["Math" => 95, "Science" => 88]
    ],
    [
        "name" => "Bob",
        "scores" => ["Math" => 78, "Science" => 92]
    ]
];

//Access elements (access Bob's Science scores)
echo $students[1]["scores"]["Science"]; // Output: 92

Common array operation functions

PHP provides hundreds of built-in functions for working with arrays. Here are some of the most commonly used ones:

• count($array): Counts the number of elements in the array.
• print_r($array): Displays the structure and values ​​of an array in a human-readable format (usually used for debugging).
• array_push($array, $value1, ...): Push (add) one or more elements to the end of the array.
• array_pop($array): Pops (removes and returns) the last element in the array.
• array_keys($array): Returns a new array composed of all key names in the array.
• array_values($array): Returns a new array consisting of all the values ​​in the array.
• in_array($needle, $haystack): Check if a specific value exists in the array.
• array_key_exists($key, $array): Check if a specific key exists in the array.

Array iteration (Looping)

Commonly usedforeachLoop through all elements in the array:

$staff = ["Manager" => "Zhang San", "Engineer" => "Li Si", "Designer" => "Wang Wu"];

// Traverse the associative array (get keys and values)
foreach ($staff as $title => $name) {
    echo $title . ": " . $name . "<br>";
}

// Traverse the indexed array (only get values)
$items = ["A", "B", "C"];
foreach ($items as $item) {
    echo $item . "<br>";
}

PHP string comparison ignores case

strcasecmp()

<?php
$str1 = "Hello";
$str2 = "hello";

if (strcasecmp($str1, $str2) === 0) {
    echo "Strings are equal (ignoring case)";
} else {
    echo "Strings are not equal";
}
?>

str_ireplace()

<?php
$text = "Hello World";
$result = str_ireplace("hello", "Hi", $text);
echo $result; // Output "Hi World"
?>

preg_match() with i modifier

<?php
if (preg_match("/hello/i", "HeLLo PHP")) {
    echo "Comparison successful";
}
?>

PHP path string processing

When processing file path strings in PHP, handwritten string slicing (such as usingexplode), because different operating systems (Windows uses\, for Linux/) are handled differently. PHP has several powerful functions built in to safely disassemble paths.

1. pathinfo() — the most versatile tool

This is my most recommended function. It can disassemble the path into: directory name, complete file name, file extension, and file name without extension.

$path = "/var/www/html/assets/img/logo.png";
$info = pathinfo($path);

echo $info['dirname']; // /var/www/html/assets/img
echo $info['basename']; // logo.png
echo $info['extension']; // png
echo $info['filename']; // logo (PHP 5.2+ supported)

2. basename() and dirname() — quickly obtain partial paths

• basename：Get the "file name" portion of the path.
• dirname：Get the "directory" part of the path.

$path = "C:\projects\web\index.php";

echo basename($path); // index.php
echo basename($path, ".php"); // index (remove the specified file extension)
echo dirname($path); // C:\projects\web

3. realpath() — Get the absolute path (entity path)

It will resolve all relative path symbols (such as../or./), and returns the true absolute path on the operating system. If the file does not exist, it will be returnedfalse。

echo realpath("../../config.php");
//Output similar to: /var/www/config.php

== Common path processing scenarios

Scenario A: Cross-platform path correction

In order to ensure that no errors occur during Windows development and Linux deployment, it is recommended to uniformly convert backslashes to forward slashes:

$path = "C:\User\Admin\Desktop\test.txt";
$safe_path = str_replace('\\', '/', $path);
// Result: C:/User/Admin/Desktop/test.txt

Scenario B: Merge paths (to prevent extra slashes)

Manual splicing$dir . '/' . $fileprone to appear//Double slash error. Can be usedDIRECTORY_SEPARATOR(system delimiter) orrtrim：

$dir = "/var/www/html/";
$file = "index.php";

//Universal splicing method
$full_path = rtrim($dir, '/\\') . DIRECTORY_SYSTEM_SEPARATOR . $file;

Scenario C: Check whether the file extension is legal

$allowed = ['jpg', 'png', 'gif'];
$ext = strtolower(pathinfo($filename, PATHINFO_EXTENSION));

if (in_array($ext, $allowed)) {
    echo "Correct format";
}

== Summary comparison table

== Get the top-level directory of the path (Root Directory Name)

To get the exact top-level directory name from a path string (e.g.var), the most robust method is to first convert the pathnormalization, and then useexplode()Deconstruct the string. Since the path usually starts with a slash, the first element of the disassembled array is often empty, which requires special handling.

Method 1: Use explode to disassemble (the most intuitive)

This is the most common way, throughltrim()Remove the leading slash before splitting, and make sure the first position in the array is the name you want.

$path = "/var/www/html/assets/img/logo.png";

// 1. Remove the leftmost slash first to avoid the empty first element produced by explode
// 2. Split into arrays according to slashes
$parts = explode('/', ltrim($path, '/'));

// 3. Get the first element of the array
$rootDir = $parts[0];

echo $rootDir; // Output: var

Method 2: Cross-platform universal processing (the most robust)

If your path may come from Windows or Linux, it is recommended to unify the slash format first and filter out duplicate slashes.

$path = "/var/www/html/assets/img/logo.png";

//Convert to forward slashes uniformly and filter out empty elements
$parts = array_values(array_filter(explode('/', $path)));

$rootDir = $parts[0] ?? '';
echo $rootDir; // Output: var

Method 3: Obtain Web Root for the "current execution environment"

If you don't want to process "specific strings", but want to know the root folder name of the web server, you can use$_SERVER：

// Assume DOCUMENT_ROOT is /var/www/html
$rootParts = explode('/', ltrim($_SERVER['DOCUMENT_ROOT'], '/'));
echo $rootParts[0]; // Output: var

== Process logical comparison table

Tips

When working with paths, be sure to pay attention to whether there is a slash at the beginning of the path."/var"After splitting it will become["", "var"],and"var"After splitting it will become["var"]. useltrim($path, '/')This ensures that the result is consistent regardless of whether there is a slash at the beginning.

PHP include path priority

PHP gets current page name

Use $_SERVER['PHP_SELF']

can pass through$_SERVER['PHP_SELF']Get the file path of the current execution and then usebasenameGet file name:

<?php
$current_page = basename($_SERVER['PHP_SELF']);
echo "Current page name:" . $current_page;
?>

Use $_SERVER['REQUEST_URI']

through$_SERVER['REQUEST_URI']Get the full URL path and then useparse_urlandbasenameParse file name:

<?php
$url_path = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
$current_page = basename($url_path);
echo "Current page name:" . $current_page;
?>

Distinguish between file names and additional parameters

If the URL contains query parameters, they can be processed separately:

<?php
$url_path = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
$query_string = parse_url($_SERVER['REQUEST_URI'], PHP_URL_QUERY);
$current_page = basename($url_path);

echo "File name:" . $current_page . "<br>";
echo "Query parameters:" .$query_string;
?>

Application examples

Assume the current URL ishttps://example.com/page.php?id=123：

Current page name: page.php
File name: page.php
Query parameters: id=123

PHP gets the current page and entry page

In PHP, whenmain.phpuseincludeintroducesubpage.phpAt this time, the two files are actually "merged and executed". To obtain the "main program path" and "introduced file path" respectively, you need to use different super-global variables and constants.

1. Get the path of "current file" (subpage.php)

Regardless of who imported the file, use the magic constant__FILE__Always points to the path of "the file where this code resides".

//Writing in subpage.php
$thisFilePath = __FILE__;
echo "Current file path: " . $thisFilePath;
//Output similar to: /var/www/html/fullpath/subpage.php

2. Obtain the path of "main program" (main.php)

when you aresubpage.phpWhen trying to figure out who the original entry point was, there are a few ways:

• Method A: Use$_SERVER['SCRIPT_FILENAME'](most accurate)
  This variable will store the absolute path where the script was originally executed.

  $mainPath = $_SERVER['SCRIPT_FILENAME'];

• Method B: Useget_included_files()(advanced tracking)
  This will return an array, indexed0This is the initial entry file.

  $allFiles = get_included_files();
  $mainPath = $allFiles[0];

3. Code integration example

Please put the following code in yoursubpage.phpMedium test:

<?php
// 1. The path to the file itself that is introduced
$sub_page_path = str_replace('\\', '/', __FILE__);

// 2. The path of the main execution file
$main_page_path = str_replace('\\', '/', $_SERVER['SCRIPT_FILENAME']);

echo "Subpage Path: " . $sub_page_path . "<br>";
echo "Main Page Path: " . $main_page_path . "<br>";
?>

Tips: str_replace('\\', '/', ...)It is to unify the path formats of Windows (backslash) and Linux (forward slash), which is very practical in cross-platform development.

== Extension: Get URL Path

If you are not referring to the server hard drive path (Full Path), but the URL path on the browser, you should use:

Suggestions for using paths

Writing$mainTableView__whereclause, if you need to switch SQL conditions based on different main pages, you can write like this:

if (basename($_SERVER['SCRIPT_FILENAME']) == 'main.php') {
    // Logic that is only executed when entering from main.php
}

Variable passing of PHP file references

1. Clarificationincludethe essence of

In PHP, useincludeorrequire, you can think of it asDirectly "copy and paste" the code imported into the file into the current file. Therefore, both will share the same execution environment (Scope).

2. Frequently Asked Questions: Is it necessary?global？

it's up to youlocation of call variable：

• Case 1: Used globally (no global required)
  if you aremain.phpDefine variables and put them inlibrary.phpThe outermost layer uses it directly without any additional declaration.

  // main.php
  $var1 = "Apple";
  include 'library.php';
  
  // library.php
  echo $var1; // Output: Apple

• Case 2: Access within a function (requires global)
  If the variable is defined in the global scope, butlibrary.phpinsideFunctionTo access it, you must declare it.

  // library.php
  function printVar() {
      global $var1; 
      echo $var1;
  }
          

3. Correction:include_oncemisunderstanding of passing parameters

Special attention:PHPinclude_once Not supportedPass a second argument (like an array). Its only parameter is the file path string.

== Recommended Best Practices

In order to avoid variable naming conflicts (namespace pollution), it is recommended to abandon the "directly dependent on global variables" writing method and use the following two methods instead:

Method A: Function parameter passing (most flexible)

Willlibrary.phpAs a pure toolbox, only functions are written in it, and variables are passed in through parameters.

// library.php
<?php
function processStock($name) {
    return "Processing stocks: " . $name;
}
?>

// main.php
<?php
include_once 'library.php';
echo processStock("TSLA"); // Pass variables explicitly
?>

Method B: Using categories and static methods (the most professional)

This is more common in modern PHP development (such as Laravel concepts) and can effectively organize the code.

// library.php
class StockTool {
    public static function handle($var) {
        return "Result: " . $var;
    }
}

// main.php
include_once 'library.php';
echo StockTool::handle($var1);

Core conclusion

1. don't wantexistincludePassing parameters in the statement is invalid.
2. Try to avoid global, use insteadfunction parametersPass, so that the code is easier to debug and maintain.

PHP variable setting check

In PHP, there are three main core functions to check whether a variable has been set (defined):isset()、empty()andarray_key_exists(). Their operating logic is slightly different, and choosing the wrong one may lead to logic holes.

1. isset() — the most commonly used check

used to determine variablesHas it been declaredandIts value is notNULL。

$var = "Gemini";
if (isset($var)) {
    echo "The variable has been set and is not NULL";
}

• Notice:If the variable is set to$var = null;，isset($var)Will send backfalse。

2. empty() — Check whether it is an "empty value"

Used to determine whether a variabledoes not exist, or its value is equivalent tofalse. it is equivalent to!isset($var) || $var == false。

The following values ​​will beempty()regarded astrue：

• ""(empty string)
• 0(integer 0)
• 0.0(floating point number 0)
• "0"(String 0)
• null
• false
• [](empty array)

3. Suggestions for practical application scenarios

== for include case

If you are inmain.phpPass variables tolibrary.php, it is recommended tolibrary.phpDo internal error-proofing checks:

Writing method A: Use isset to prevent errors

// library.php
if (isset($var1)) {
    echo "The received variable is:" . $var1;
} else {
    echo "Warning: Variable var1 is not defined yet.";
}

Writing method B: Use Null coalescing operator (PHP 7+) — Recommended

This is a more concise way of writing it. If the variable is not set, it is given a default value.

// If $var1 is not set, $data is equal to 'default value'
$data = $var1 ?? 'Default value';

Writing method C: Check GET/POST parameters

If you pass the value from the front end, the check method is as follows:

if (isset($_GET['var1'])) {
    $v1 = $_GET['var1'];
}

Tips:During the development phase, it is recommended to adderror_reporting(E_ALL);, so that if you access an undefined variable, PHP will directly spit outNotice: Undefined variableMind you.

PHP’s debug_backtrace()

use

debug_backtrace()It is a function used by PHP to obtain the current execution stack (call path). It is often used for debugging and recording call sources.

Basic usage

$trace = debug_backtrace();
print_r($trace);

Return structure description

debug_backtrace()An array will be returned, arranged in the order of the call:

• [0]:Current file (current function or included file)
• [1]: the source from which it is called (upper-level file or function)
• [2]、[3]...: Higher-level call

Common fields

• file:File path
• line:Program line number
• function：The function name called
• class: Category name (if any)
• args: Pass in parameters

Example: Get the file path of the previous layer

function showCaller() {
    $trace = debug_backtrace();
    echo 'From: ' . $trace[1]['file'] . ' No. ' . $trace[1]['line'] . ' line';
}

include 'subpageA.php'; // Call showCaller() within subpageA.php

Example: Multi-level inclusion situations

• main.php include subA.php
• subA.php include subB.php
• subB.phpuse:

$trace = debug_backtrace();
echo 'Current file:' . $trace[0]['file'] . "\n";
echo 'Previous level:' . $trace[1]['file'] . "\n"; // subA.php
echo 'Homepage:' . $trace[2]['file'] . "\n"; // main.php

summary

• debug_backtrace()Is the most practical way to view the source of include/function calls
• Suitable for debugging, recording, permission checking and other needs

PHP error_log

use

Basic usage

<?php
error_log("This is a test message");
?>

Record variable content

<?php
$data = ["a" => 1, "b" => 2];
error_log(print_r($data, true));
?>

Specify the file to write to

<?php
error_log("Write custom file", 3, "D:/logs/php_debug.log");
?>

Record error level

<?php
error_log("[INFO] program starts execution");
error_log("[WARN] parameter is empty");
error_log("[ERROR] Database connection failed");
?>

Error log location

log_errors = On
error_log = "D:/logs/php_errors.log"

• Linux: Write to Web Server error log
• Windows: Write to system or Apache error log

Handling with exceptions

<?php
try {
    throw new Exception("Exception occurred");
} catch (Exception $e) {
    error_log($e->getMessage());
}
?>

Common uses

• No output to the screen when debugging (to avoid breaking JSON/API postbacks)
• Record user operations or system status
• Formal environment tracking error source

Things to note

• Please make sure the log directory has write permissions
• Avoid recording sensitive information (passwords, tokens)
• Official environment recommends closingdisplay_errors, just useerror_log

PHP error log Chinese processing

When you use error_log() in PHP to record strings containing Chinese characters, the log file will often appear in hexadecimal encoding such as \xe6\xb2\x92 format. This is usually not a programming error, but the result of the server (Apache/Nginx) forcing non-ASCII characters to be escaped for security or compatibility reasons.

Solution 1: Use a custom log function (most recommended)

This is the simplest and most effective way to do it. By directly manipulating files, the server's filtering mechanism for error_log() can be bypassed.

function write_utf8_log($message) { $log_file = DIR . '/debug.log'; $timestamp = date('Y-m-d H:i:s'); // Use FILE_APPEND mode to write raw bytes file_put_contents($log_file, "[$timestamp] $message" . PHP_EOL, FILE_APPEND | LOCK_EX); }

// Calling example $title = $_GET["title"]; write_utf8_log("Title content: " . $title);

Solution 2: Force unescaped Unicode encoding

If you want to retain the path setting of error_log(), you can use json_encode with the JSON_UNESCAPED_UNICODE parameter. This will force PHP to output in UTF-8 format, but it may still be escaped twice in some server environments.

 $title = $_GET["title"]; error_log('title: ' . json_encode($title, JSON_UNESCAPED_UNICODE)); 

Solution 3: Modify server log configuration

If you are using Apache 2.4+, you can try modifying ErrorLogFormat to adjust the escaping behavior of log output.

1. Define the format in the Apache configuration file (such as httpd.conf):

 ErrorLogFormat "[%t] [%l] [pid %P] %F: %E: [client %a] %M" 

2. Make sure the operating system language supports UTF-8. Modify /etc/apache2/envvars in Ubuntu:

 export LANG=en_US.UTF-8 export LC_ALL=en_US.UTF-8 

Solution 4: Decoding techniques for temporary viewing

If the log has been generated and you cannot change the server settings, you can use the following method to view the original Chinese:

• Terminal instant decoding:Use tail with the sed command to convert \x into a bash readable format.
• Base64 relay:First execute base64_encode($title) in PHP and then record, and then manually decode when viewing to ensure that the data is not damaged due to escaping.

Summary comparison

Parse URL query string names and values

Get query string

$url = "https://example.com/page.php?name=John&age=30&lang=php";
$query = parse_url($url, PHP_URL_QUERY); // The result is "name=John&age=30&lang=php"

Parse query string into key-value pairs

parse_str($query, $params);

[
  "name" => "John",
  "age" => "30",
  "lang" => "php"
]

Complete example

<?php
$url = "https://example.com/page.php?name=John&age=30&lang=php";
$query = parse_url($url, PHP_URL_QUERY);
parse_str($query, $params);

foreach ($params as $key => $value) {
    echo "$key = $value\n";
}
?>

Execution result

name = John
age = 30
lang = php

Things to note

• parse_url()Only the query part will be retrieved and the content will not be parsed.
• parse_str()Can handle URL encoding, e.g.%20will be converted to spaces.
• Using the second argument to receive the result array avoids writing the variable to the global namespace.
• Supports array formats such astags[]=php&tags[]=htmlwill be converted into an array.

PHP gets the content of a certain tag

Method 1: Use JavaScript

Get using JavaScript<h1>content and then send it to PHP:

<!DOCTYPE html>
<html lang="zh-Hant">
<head>
<meta charset="UTF-8">
<title>Get H1 content</title>
<script>
    function sendH1Content() {
        var h1Content = document.querySelector('h1').innerText;
        var xhr = new XMLHttpRequest();
        xhr.open('POST', 'process.php', true);
        xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
        xhr.send('h1Content=' + encodeURIComponent(h1Content));
    }

    window.onload = sendH1Content;
</script>
</head>
<body>
<h1>This is the title of the page</h1>
</body>
</html>

PHP side processing

existprocess.phpReceive and process H1 content in:

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
$h1Content = $_POST['h1Content'] ?? '';
// Process $h1Content, such as storing it in the database or performing other operations
echo "Received H1 content: " . htmlspecialchars($h1Content);
}
?>

Method 2: Use server-side parsing

If the HTML file is static, you can use PHP to read the file and parse it:

<?php
$htmlContent = file_get_contents('path/to/your/file.html');

preg_match('/<h1>(.*?)<\/h1>/', $htmlContent, $matches);
$h1Content = $matches[1] ?? '';

// handle $h1Content
echo "H1 content: " . htmlspecialchars($h1Content);
?>

Summarize

The most common way is to use JavaScript to get the content on the client side and then send it to PHP for processing via AJAX. Server-side parsing is typically used for static content and is not recommended for dynamically generated pages.

Get the content of the last tag on the homepage

illustrate

Method 1: Pass in variables (best and most commonly used)

<!-- abc.php -->
<h2>AAA</h2>
<h2>BBB</h2>
<h2>lasth2</h2>

<?php
$last_h2 = "lasth2";
include "subpage.php";
?>

<!-- subpage.php -->
<?php
echo "The last H2 on the homepage is: " . $last_h2;
?>

Method 2: Use the output buffer to capture the output HTML (advanced)

<!-- abc.php -->
<?php
ob_start(); // Start buffering
?>

<h2>AAA</h2>
<h2>BBB</h2>
<h2>lasth2</h2>

<?php
$html = ob_get_clean(); // Get all output and clear the buffer

preg_match_all('/<h2>(.*?)<\\/h2>/i', $html, $matches);
$last_h2 = end($matches[1]); //The content of the last h2

include "subpage.php";

//Finally print out the original HTML
echo $html;
?>

Method 3: Put all h2 into the array and specify the last one before include

<!-- abc.php -->
<?php
$h2_list = ["AAA", "BBB", "lasth2"];
?>

<h2>AAA</h2>
<h2>BBB</h2>
<h2>lasth2</h2>

<?php
$last_h2 = end($h2_list);
include "subpage.php";
?>

in conclusion

• best way: Pass "the content of the last h2" into subpage.php as a variable before include
• If you really need to grab HTML from the output → useob_start()+ Regular expression parsing

PHP urlencode()

urlencode()Function is used to URL encode (Percent-encoding) a string. When passing data as URL parameters, this is a required step to ensure that all special characters are transferred and parsed correctly.

Function definition and usage

string urlencode(string $string): string

This function converts the given string into a URL-safe format. It replaces all non-alphanumeric characters except the minus sign (-), bottom line (_), period (.) and tilde (~) outside.

Replaced special characters will be replaced with percent signs (%) followed by the two-digit hexadecimal representation of the character's ASCII value (for example, a space $\rightarrow$%20）。

Why is URL encoding needed?

1. Special character conflicts:Some characters in the URL (such as?、&、=、/) has a special meaning. If these characters are included in the parameters, the browser or server may misunderstand the structure of the URL.
2. Non-ASCII character transmission:Non-ASCII characters such as Chinese, Japanese, Korean, etc. must be encoded into URL-safe byte sequences before they can be transmitted in the URL.urlencode()These characters are encoded in UTF-8 format.
3. Space handling: urlencode()will convert spaces to plus signs (+) or%20(Althoughurlencode()What is produced is+, but in URL parameters, both representations represent spaces).

PHP code example

Example 1: Special characters and Chinese encoding

$data = "PHP Array with $100 & 50% off";
$encoded_data = urlencode($data);

echo "<h3>Special characters and Chinese examples</h3>";
echo "<p>Original string: " . htmlspecialchars($data) . "</p>";
echo "<p>Encoding result: " . htmlspecialchars($encoded_data) . "</p>";

// Output results are similar: PHP+array and +%24100+%26+50%25+offer
// (Chinese 'array' will be encoded as %E9%99%A3%E5%88%97, etc.)

Example 2: Constructing a complete API query URL

Suppose you need to change the query stringq_strSecurely appended to API URL.

$api_base = "http://api.example.com/search";
$search_query = "Mobile Photography Tips (2025)";

// Ensure query string security
$encoded_query = urlencode($search_query);

//Construct the final URL
$final_url = $api_base . "?q_str=" . $encoded_query;

echo "<h3>Construction URL Example</h3>";
echo "<p>Query string: " . htmlspecialchars($search_query) . "</p>";
echo "<p>Final URL: " . htmlspecialchars($final_url) . "</p>";

// The final URL is similar: http://api.example.com/search?q_str=%E6%89%8B%E6%A9%9F%E6%94%9D%E5%BD%B1%E6%8A%80%E5%B7%A7+%282025+%E5%B9%B4%29

Comparison with rawurlencode()

PHP has another similar functionrawurlencode(), the main difference between them is the handling of spaces:

• urlencode(): Convert spaces to plus signs (+). This is typically used to encode the value of a **GET parameter** (e.g.?key=valueinvaluepart).
• rawurlencode(): Convert spaces to%20. This is consistent withRFC 3986A more restrictive definition, typically used to encode the **Path Segments** (Path Segments) of a URL, or when you need precise%20rather than+hour.

Space processing comparison example

$space_test = "This is a test";

echo "<h3>urlencode() vs rawurlencode()</h3>";
echo "<p>urlencode(): " . urlencode($space_test) . "</p>"; // Output: This+is+a+test
echo "<p>rawurlencode(): " . rawurlencode($space_test) . "</p>"; // Output: This%20is%20a%20test

PHP output buffering

Introduction

Commonly used functions

• ob_start(): Enable output buffering.
• ob_get_contents(): Get the current buffered content.
• ob_end_clean(): End buffering and clear without output.
• ob_end_flush(): End buffering and output content.
• ob_get_clean(): Get the content and end buffering.

Example: Modify output content

<?php
ob_start(); // Start output buffering

echo "Hello World!";

$content = ob_get_clean(); // Get and clear buffer content
echo strtoupper($content); // Output the modified content: HELLO WORLD!
?>

Example: Insert a unified style before all content is output

<?php
ob_start();
register_shutdown_function(function () {
    $html = ob_get_clean();
    echo "<div class='container'>" . $html . "</div>";
});
?>

<h1>Content title</h1>
<p>This is the content paragraph. </p>

use

• Automatically handle overall HTML output (e.g. compression, style wrapping)
• Prevent error messages from interfering with JSON or XML output
• Process or temporarily store the output before deciding whether to output it later
• Combine output and compress to reduce web page size

Things to note

• With buffering, header() can be called after echo since the output is not actually output yet
• Avoid multiple opening and closing buffers, otherwise it will cause confusion
• If the buffer is not ended, it may cause output delays

PHP library that automatically displays images to the right of each h2 block

Function description

How to use

<?php
ob_start();

function add_images_next_to_h2($html) {
    $pattern = '/(<h2.*?>.*?<\/h2>)(.*?)(?=<h2|\z)/is';
    $index = 1;
    return preg_replace_callback($pattern, function($matches) use (&$index) {
        $h2 = $matches[1];
        $body = $matches[2];
        $imgPath = "/images/h2-$index.jpg";
        $imgFile = $_SERVER['DOCUMENT_ROOT'] . $imgPath;

        if (file_exists($imgFile)) {
            $output = "<div style='display: flex; align-items: flex-start; gap: 20px; margin-bottom: 1.5em;'>";
            $output .= "<div style='flex: 1;'>" . $h2 . $body . "</div>";
            $output .= "<img src='$imgPath' style='max-width: 200px; height: auto; border: 1px solid #ccc;'>";
            $output .= "</div>";
        } else {
            $output = $h2 . $body;
        }

        $index++;
        return $output;
    }, $html);
}

register_shutdown_function(function() {
    $html = ob_get_clean();
    echo add_images_next_to_h2($html);
});
?>

Drawing preparation

• /images/h2-1.jpg
• /images/h2-2.jpg
• /images/h2-3.jpg

Example usage

<?php include "h2-image-right.php"; ?>

<h2>First paragraph title</h2>
<p>This is the content of the first paragraph. </p>

<h2>Second paragraph title</h2>
<p>This is the content of the second paragraph. </p>

Things to note

• The order of the pictures is according to<h2>The order of appearance corresponds to that, please name accordingly.
• This method wraps<h2> ~ Content belowIt is a flex block, suitable for pure content pages.
• If it conflicts with the use of other output buffers, please make sure not to repeat it.ob_start()。

Check if the traffic source is coming from search engine bots

1. Use server logs

Checking server logs is an important way to identify search engine bots. Here are some examples of User-Agent for search engine robots:

• Googlebot: Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
• Bingbot: Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)
• Baidu Spider: Mozilla/5.0 (compatible; Baiduspider/2.0; +http://www.baidu.com/search/spider.html)

2. Use robots.txt file

Check the websiterobots.txtFile that lets you learn which search engine robots are allowed or blocked from accessing certain parts of your website. For example:

User-agent: * 
Disallow: /private/

3. Determine the IP address

Search engine bots usually have IP addresses from a specific range. You can compare whether the visitor's IP address falls within these ranges. For example:

• Googlebot IP address range
• Bingbot’s IP address range

Tools can be used to verify whether the visitor's IP actually comes from a search engine.

4. Use backend code to make judgments

The following is an example of how to use PHP on the server side to perform User-Agent checking:

<?php
$userAgent = $_SERVER['HTTP_USER_AGENT'];
if (strpos($userAgent, 'Googlebot') !== false) {
    echo "This is Googlebot traffic";
} else {
    echo "This is not search engine robot traffic";
}
?>

5. Monitoring and Analysis Tools

Use Google Analytics or other website analytics tools to help track traffic sources. These tools typically filter most bot traffic automatically.

Hash value of URL

1. Definition

The hash value of a URL refers to the part after the "#" symbol in the URL, also known as the fragment identifier (Fragment Identifier). It is typically used to identify a location or state within a page.

2. Purpose

• Navigate to a specific location in a web page, such as an anchor.
• Represents the state of an application, such as a route for a single-page application (SPA).
• Used to store user interface state, such as filter conditions or scroll position.

3. Example

Here are some common URL Hash examples:

• Anchor navigation:https://example.com/page#section1
• SPA routing:https://example.com/app#/dashboard
• Status saving:https://example.com/search#filter=active

4. Working principle

1. When the browser encounters a hash value in the URL, it does not send this part of the data to the server.
2. Hash values ​​are processed by the client (usually JavaScript) and used to trigger specific logic or actions.
3. In HTML, Hash can be used to locate theid。

5. Precautions

• Hash does not affect HTTP requests, so it can be modified dynamically without reloading the page.
• In SPA, applications need to manually parse and process Hash values ​​to implement routing functionality.
• Avoid overly complex Hash value design and keep the structure simple and clear.

Get the Hash value of the URL

JavaScript example

<script>
  // Get the Hash value of the URL
  const hashValue = window.location.hash.substring(1);

  //Display Hash value
  console.log("Hash value is:", hashValue);
</script>

PHP example

<?php
//Mock URL
$url = "http://example.com/page#section2";

// Use parse_url to parse Hash values
$parsedUrl = parse_url($url);
$hash = isset($parsedUrl['fragment']) ? $parsedUrl['fragment'] : null;

// Output Hash value
if ($hash) {
    echo "The Hash value is: " . htmlspecialchars($hash, ENT_QUOTES, 'UTF-8');
} else {
    echo "There is no Hash part in the URL.";
}
?>

Things to note

• JavaScript can directly obtain the Hash value of the current page, usingwindow.location.hash。
• The server cannot directly obtain the hash of the URL and needs to be sent to the server through JavaScript.

Link to a specific tag without using an id

Method 1: Usenameproperty

Although less commonly used, it is possible tonameAdd an attribute<a>tag and place it before the target tag.

<a name="specific-heading1"></a>
<h3>Target title 1</h3>

<a href="#specific-heading1">Link to specific heading</a>

Effect:

Target title 2

Method 2: Usedata-attributeWith JavaScript

By setting custom properties, such asdata-anchor, and use JavaScript to handle the jump behavior.

<h3 data-anchor="heading-1">Target heading 3</h3>

<a href="#" onclick="jumpToHeading('heading-1')">Link to specific heading</a>

<script>
  function jumpToHeading(anchor) {
    const target = document.querySelector(`[data-anchor="${anchor}"]`);
    if (target) {
      target.scrollIntoView({ behavior: 'smooth' });
    }
  }
</script>

Effect:

Goal title 4

Method 3: Useh2text content with JavaScript

by searchh2text content to target, using JavaScript to dynamically target the target.

<h3>Target title 5</h3>

<a href="#" onclick="jumpToText('Target Title')">Link to specific title</a>

<script>
  function jumpToText(text) {
    const target = Array.from(document.querySelectorAll('h2')).find(el => el.textContent === text);
    if (target) {
      target.scrollIntoView({ behavior: 'smooth' });
    }
  }
</script>

Effect:

Goal title 6

cURL

use

cURL is a library used in PHP to send HTTP requests. It supports GET, POST, PUT, DELETE and other methods, and is often used for API data access.

Basic steps

1. initialization:curl_init()
2. Setting options:curl_setopt()
3. Execute request:curl_exec()
4. Close the connection:curl_close()

GET example

<?php
$url = "https://api.example.com/data";
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);
echo $response;
?>

POST example

<?php
$url = "https://api.example.com/post";
$data = ['name' => 'Test', 'email' => '[email protected]'];
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);
echo $response;
?>

Plus headers with JSON

<?php
$url = "https://api.example.com/json";
$data = json_encode(['id' => 123]);
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
  'Content-Type: application/json',
  'Content-Length: ' . strlen($data)
]);
$response = curl_exec($ch);
curl_close($ch);
echo $response;
?>

Common options

• CURLOPT_URL: Set destination URL
• CURLOPT_RETURNTRANSFER: Whether to return the result (not output directly)
• CURLOPT_POSTFIELDS:Sent information
• CURLOPT_HTTPHEADER: Custom HTTP headers

Error handling

<?php
if(curl_errno($ch)) {
  echo 'Error:' . curl_error($ch);
}
?>

PHP check network port

In PHP, check whether a specific network port (Port) is listening, usually to confirm whether the local or remote service is running and accepting connections. The most common method is to use Socket related functions to try to establish a TCP connection.

Use the fsockopen() function (recommended for remote inspection)

fsockopen()Function is used to open a network connection or Unix domain Socket connection. If the connection is successful, it means that the port is listening; if the connection fails, it usually means that the port is not open or blocked by a firewall.

PHP code example

/**
 * Check if the port on the specified IP/hostname is listening
 *
 * @param string $host The host name or IP address to check
 * @param int $port The port number to be checked
 * @param int $timeout Connection timeout seconds
 * @return bool If the connection is successful, return true; otherwise return false
 */
function is_port_listening(string $host, int $port, int $timeout = 2): bool {
    // Establish a Socket connection. The @ symbol is used to suppress connection error messages.
    $connection = @fsockopen($host, $port, $errno, $errstr, $timeout);

    if (is_resource($connection)) {
        // If $connection is a resource type, it means the connection is successful
        fclose($connection); //Close the connection immediately after success
        return true;
    } else {
        // The connection failed. The port may not be open or the service may not be running.
        // Optional: You can print $errstr and $errno here for debugging
        // echo "Connection failed: $errstr ($errno)<br>";
        return false;
    }
}

// --- Test example ---
$remote_host = 'www.google.com';
$remote_port = 80; // Check Google's HTTP port

$local_host = '127.0.0.1';
$local_web_port = 80; // Check the port of the local web server
$unoccupied_port = 65432; // Assume this port is not in use

echo "<h3>Port monitoring check results</h3>";

// Check the remote service
if (is_port_listening($remote_host, $remote_port)) {
    echo "<p>{$remote_host}:{$remote_port} is listening (connection successful).</p>";
} else {
    echo "<p>{$remote_host}:{$remote_port} is not open or the connection failed.</p>";
}

// Check the local web server (if your web server is running on port 80)
if (is_port_listening($local_host, $local_web_port)) {
    echo "<p>{$local_host}:{$local_web_port} is listening (Web server running).</p>";
} else {
    echo "<p>{$local_host}:{$local_web_port} is not listening.</p>";
}

// Check for an unoccupied port
if (is_port_listening($local_host, $unoccupied_port)) {
    echo "<p>{$local_host}:{$unoccupied_port} is listening.</p>";
} else {
    echo "<p>{$local_host}:{$unoccupied_port} is not listening (expected result).</p>";
}

Using the Socket library (lower level control)

If you need lower-level Socket operations (such as setting options, non-blocking mode, etc.), you can use PHP's Socket function library (need to enablephp_socketsextension).

function is_port_listening_socket(string $host, int $port): bool {
    // Create a TCP/IP Socket
    $socket = @socket_create(AF_INET, SOCK_STREAM, SOL_TCP);

    if ($socket === false) {
        // echo "socket_create failed: " . socket_strerror(socket_last_error()) . "<br>";
        return false;
    }

    //Try to connect
    // socket_connect() will try to establish a connection on the specified host and port
    $result = @socket_connect($socket, $host, $port);

    socket_close($socket);

    return ($result !== false);
}

Notes and limitations

• Connection timeout (Timeout):Be sure to set a reasonable$timeoutvalue (e.g. 2-5 seconds). Without this setting, your script may block for a long time when the target host is unreachable.
• Firewall:If you check the remote port, even if the service is running, if the target server's firewall blocks your connection,fsockopen()It will still fail.
• `allow_url_fopen`： fsockopen()Functions are generally not included in PHP configuration filesallow_url_fopenA limitation of the command because it operates directly on network Sockets.
• Local port check:To check if a native service is listening, you would typically$hostset to127.0.0.1orlocalhost。

PHP gets Web API results

In PHP, to get the results of a Web API and parse JSON, you typically usefile_get_contents()or cURL library to send HTTP requests, and then usejson_decode()Function to parse the returned JSON string.

Use file_get_contents() to get API results

For a simple GET request,file_get_contents()is a quick method. But if the API requires specific HTTP headers or more complex requests, cURL is more suitable.

PHP code example (GET request)

$api_url = 'https://jsonplaceholder.typicode.com/posts/1'; // Sample API URL

// Get the content returned by the API (JSON format string)
$json_data = @file_get_contents($api_url);

if ($json_data === FALSE) {
    echo "Unable to obtain API data or API request failed.";
} else {
    // Parse JSON string into PHP array or object
    // The second parameter is set to true and it will be parsed into an associative array.
    // Set to false (default) to parse into an object.
    $data = json_decode($json_data, true);

    if ($data === null && json_last_error() !== JSON_ERROR_NONE) {
        echo "JSON parsing error:" . json_last_error_msg();
    } else {
        echo "<h3>API return data (associated array)</h3>";
        //Example: access specific fields in data
        echo "<p>title (title): " . htmlspecialchars($data['title']) . "</p>";
        echo "<p>Content (body): " . htmlspecialchars($data['body']) . "</p>";

        // Output the complete structure for inspection
        echo "<h4>Complete data structure (print_r)</h4>";
        echo "<pre>";
        print_r($data);
        echo "</pre>";
    }
}

Use cURL to get API results (suitable for complex requests)

cURL provides more control, such as setting request methods (POST, PUT, DELETE), headers, timeouts, etc.

PHP code example (cURL GET request)

$api_url = 'https://jsonplaceholder.typicode.com/posts/2';

//Initialize cURL session
$ch = curl_init();

//Set cURL options
curl_setopt($ch, CURLOPT_URL, $api_url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); // Return the result as a string instead of outputting it directly

//Execute cURL session and get the results
$json_data = curl_exec($ch);

// Check if an error occurred
if (curl_errno($ch)) {
    echo "cURL error:" . curl_error($ch);
    $data = null;
} else {
    // Parse JSON
    $data = json_decode($json_data, true);
    
    if ($data === null && json_last_error() !== JSON_ERROR_NONE) {
        echo "JSON parsing error:" . json_last_error_msg();
    }
}

// Close cURL session
curl_close($ch);

if ($data !== null) {
    echo "<h3>API return data (cURL example)</h3>";
    echo "<p>title (title): " . htmlspecialchars($data['title']) . "</p>";
    echo "<p>User ID (userId): " . htmlspecialchars($data['userId']) . "</p>";
}

JSON parsing function: json_decode()

json_decode($json_string, $associative)

• $json_string: JSON format string to be parsed.
• $associative: Bollinger value. if fortrue, then return the associated array; iffalse(default), the object is returned.

PHP exec() asynchronous execution

PHPexec()function andshell_exec()、system()Similarly, it is essentially synchronous blocking, that is, the PHP script will wait for the external command to complete before continuing. To execute external commands without blocking the main PHP program (implementing "asynchronous" or "background execution"), we must rely on the characteristics of the Shell itself to separate the commands.

The core principle of implementing asynchronous exec()

The key to achieving non-blocking execution is when you passexec()Add specific Shell syntax to the command string:

1. **Background execution symbol&:** This is the core symbol for pushing commands to background execution.
2. **Output redirection> /dev/null 2>&1:** This is key to preventing PHP from blocking. It redirects both standard output (STDOUT) and standard error output (STDERR) to an empty device/dev/null. Without redirection, even if using&symbol, some versions of PHP may still wait for the I/O stream to close, causing spurious blocking.
3. **Detach processnohup(Optional but recommended): ** On Linux/Unix systems, usenohupThis ensures that the process continues to run after the web server terminates, such as when the HTTP request ends or the user closes the browser.

PHP code example (Linux/Unix-like systems)

Example 1: Basic asynchronous execution

This example is suitable for short-lived background tasks that do not need to run after the HTTP request is completed.

$command_to_run = 'php /path/to/my_long_task.php arg1 arg2';

// Combine non-blocking commands
// 1. The command itself
// 2. Direct STDOUT to /dev/null
// 3. Direct STDERR (2) to STDOUT (&1)
// 4. Use the & symbol to push the background
$async_command = $command_to_run . ' > /dev/null 2>&1 &';

$output = [];
$return_var = 0;

//Execute non-blocking commands
exec($async_command, $output, $return_var);

echo "<h3>Asynchronous execution result (exec)</h3>";
echo "<p>The command has been sent to background execution.</p>";
echo "<p>PHP scripts will continue execution immediately and will not wait for external scripts to complete.</p>";
echo "<p>The output array (\$output) returned by exec() will be almost empty.</p>";

Example 2: Use nohup to achieve process separation (recommended for long tasks)

This example usesnohupTo ensure that background tasks are completely separated from the PHP web server's parent process, the tasks will continue to run even if the web server is shut down.

$command_to_run = '/usr/bin/python3 /path/to/process_data.py';
$log_file = '/var/log/my_app/task_log.log'; // Special log file

// Ensure command parameters are properly escaped to prevent shell injection attacks
$safe_command = escapeshellcmd($command_to_run);

// Direct output and error output to the log file instead of /dev/null
$detached_command = 'nohup ' . $safe_command . ' >> ' . escapeshellarg($log_file) . ' 2>&1 &';

exec($detached_command);

echo "<h3>Use nohup to detach the process</h3>";
echo "<p>The command was started using nohup and directed output to a log file.</p>";
echo "<p>The task will continue to run in the background until completed.</p>";

Security considerations: escaping commands and parameters

Security is the most important consideration when you execute external commands. **Never** pass unsanitized or escaped user input toexec()or other shell executable functions. PHP provides two functions to assist in processing:

• escapeshellcmd($command): Escape **the entire command string** to prevent malicious users from inserting multiple commands.
• escapeshellarg($arg):Escape **single parameter** to ensure that the parameter is treated as a single string.

$user_input = "test; rm -rf /"; // Potentially malicious input

// Error: Unsafe practice
// exec('my_script.sh ' . $user_input);

// Correct: safe approach
$safe_input = escapeshellarg($user_input);
$safe_command = 'my_script.sh ' . $safe_input;
//Execution result: my_script.sh 'test; rm -rf /' (treated as a single parameter)

PHP calls Python

concept

• exec()
• shell_exec()
• passthru()
• proc_open()(Advanced)

Basic usage: shell_exec

<?php
$cmd = "python3 myscript.py 123";
$output = shell_exec($cmd);
echo $output;
?>

Pass parameters

<?php
$arg1 = 100;
$arg2 = "hello";

$cmd = "python3 script.py " . escapeshellarg($arg1) . " " . escapeshellarg($arg2);
$result = shell_exec($cmd);

echo $result;
?>

Python example

#script.py
importsys
a = sys.argv[1]
b = sys.argv[2]
print(f"Input parameters: {a}, {b}")

Get Python multiline output: exec

<?php
exec("python3 test.py", $output_lines, $status);

echo "<pre>";
print_r($output_lines);
echo "</pre>";
?>

Advanced: Use proc_open to control stdin / stdout

<?php
$descriptor = [
    0 => ["pipe", "r"],
    1 => ["pipe", "w"],
    2 => ["pipe", "w"]
];

$process = proc_open("python3 calc.py", $descriptor, $pipes);

if (is_resource($process)) {
    fwrite($pipes[0], "50\n");
    fclose($pipes[0]);

    $output = stream_get_contents($pipes[1]);
    fclose($pipes[1]);

    $error = stream_get_contents($pipes[2]);
    fclose($pipes[2]);

    proc_close($process);

    echo "Output: $output<br>";
    echo "Error: $error<br>";
}
?>

Things to note

• PHP must be able to find python3, and the absolute path can be set, such as/usr/bin/python3orC:\\Python39\\python.exe
• useescapeshellarg()Prevent command injection
• Under Windows systems, please pay attention to adding double quotes in the path.
• If long-term operations are required, it is recommended to use queue or background execution (such as systemd / supervisor)

suggestion

• PHP calls Python to do AI/ML calculations
• Two-way communication (PHP ↔ Python)
• Resident Python program for PHP query

PHP-GTK

Introduction

feature

• Use PHP to write cross-platform desktop applications.
• Supports GUI components such as buttons, text boxes, drop-down menus, tables, etc.
• Can be combined with PHP's existing function libraries, such as database access, string processing, and network functions.
• Cross-platform, supports Windows, Linux (GTK+ environment).

Installation method

• Windows: Download the PHP-GTK binary package, unzip it and use it.
• Linux: You need to install GTK+ and then compile PHP-GTK from the source code.
• Check installation: executephp -mConfirm loadingphp-gtkMods.

Sample program

<?php
if (!class_exists('gtk')) {
    die("PHP-GTK has not been installed\n");
}

$window = new GtkWindow();
$window->set_title("PHP-GTK Example");
$window->set_size_request(300, 200);
$window->connect_simple('destroy', array('Gtk', 'main_quit'));

$button = new GtkButton("Click me");
$button->connect_simple('clicked', function() {
    echo "Button clicked!\n";
});

$window->add($button);
$window->show_all();

Gtk::main();
?>

limit

• PHP-GTK has stopped updating for many years and is currently low-maintenance.
• Not suitable for large or high-performance desktop applications.
• Only supports GTK+ 2, not GTK+ 3 or 4.

Applicable situations

• Learn GUI and event-driven programming.
• Simple desktop tools such as database management gadgets.
• Want to quickly develop desktop applications using PHP syntax.

Alternatives to PHP GUI Development

current situation

alternatives

• Electron + PHPuseElectron(Based on Chromium and Node.js) Create a desktop GUI, and the backend can still call PHP programs. This allows you to build beautiful cross-platform applications using HTML/CSS/JavaScript and communicate with PHP via API.
• NW.jsSimilar to Electron, desktop applications are developed using web technology and can be combined with PHP as back-end computing.
• PHP + Web Browser (Local Web App)Start a PHP built-in server on desktop (php -S localhost:8000), Then use the browser to open the page, and it will look like a desktop application. With PWA (Progressive Web App), it can also be installed as a desktop icon.
• GUI Framework for other languagesIf the target is a desktop application rather than PHP itself, consider:
  • Python + PyQt / Tkinter / Kivy
  • Java + JavaFX / Swing
  • C# + WinForms / WPF / .NET MAUI
  These are more stable and continuously maintained than PHP-GTK.

suggestion

• If you insist on using PHP, the best solution isElectron/NW.js + PHP, The front-end is built with web technologies, and the back-end continues to use PHP, making it cross-platform and modern.
• If other languages ​​are accepted, it is recommended to use Python or C# instead, which will provide better support in the desktop development field.

single page application

A Single Page Application (SPA) is a web application or website model that interacts with users by dynamically rewriting the current page instead of loading an entire new page from the server. This approach avoids interruptions between page switches and brings the user experience closer to a desktop application.

Differences between SPA and traditional multi-page applications (MPA)

In the traditional model, each time a link is clicked, a new HTML file is requested from the server; in SPA, the necessary HTML, CSS, and JavaScript are downloaded only on the first load, and subsequent data exchange is completed through AJAX or Fetch API.

The core components of a SPA

• Front-end routing (Routing):Although there is only one HTML file, JavaScript is used to monitor URL changes (Hash or History API) and dynamically display the corresponding components.
• State Management:Share data (such as user login status, shopping cart contents) between different components.
• Dynamic rendering:Use frameworks such as Vue, React or Angular to instantly update the DOM structure based on data changes.

Simple SPA routing logic example

This is a framework-independent, using only native JavaScript to simulate the logic of SPA switching content:

<!-- index.html -->
<nav>
  <a href="#home" onclick="route()">Homepage</a>
  <a href="#trading" onclick="route()">Trading charts</a>
</nav>

<div id="content">
  <!-- Dynamic content will be injected here -->
</div>

<script>
  const routes = {
    "#home": "<h2>Welcome back</h2><p>This is your dashboard.</p>",
    "#trading": "<h2>Real-time Quotes</h2><div id='tv-container'>Chart loading...</div>"
  };

  function route() {
    const hash = window.location.hash || "#home";
    const contentDiv = document.querySelector("#content");
    contentDiv.innerHTML = routes[hash];

    // If you switch to the trading page, you can initialize the previous TradingView Widget here
    if (hash === "#trading") {
      // initTradingView();
    }
  }

  // Monitor URL changes
  window.addEventListener("hashchange", route);
  // initial load
  route();
</script>

Advantages and Disadvantages of SPA

advantage:Fast speed, reduced bandwidth consumption, and separate front-end and back-end development (the back-end only needs to provide API).
shortcoming:The initial loading time is long (First Load), and SEO needs to be compensated through SSR (server-side rendering) or pre-rendering technology.

single page application framework

When developing a single-page application (SPA), choosing an appropriate framework solution can significantly improve development efficiency and code maintainability. The current market is dominated by three mainstream frameworks, with many emerging up-and-comers.

React

Developed and maintained by Meta (Facebook), it is currently the most used UI function library in the world. It introduces Virtual DOM (Virtual DOM) and JSX syntax, emphasizing componentization and one-way data flow.

• advantage:The ecosystem is extremely large, the community resources are abundant, and the job market demand is huge.
• Commonly used combinations:React Router (routing), TanStack Query (data acquisition), Zustand/Redux (state management).

Vue.js

Developed by You Yuxi, it is famous for its "progressive" framework. Its learning curve is relatively gentle, and the official provides a very complete tool chain, which is very suitable for projects that pursue development efficiency.

• advantage:High file affinity, two-way data binding, and intuitive syntax.
• Commonly used combinations:Vue Router (routing), Pinia (state management), Vite (construction tool).

Angular

A complete framework maintained by Google, written in TypeScript. It provides a "Family Bucket" solution, including all necessary functions such as routing, form verification, and HTTP clients.

• advantage:The rigorous architecture is suitable for large-scale enterprise-level projects and has built-in dependency injection (DI).
• Commonly used combinations:RxJS (reactive programming).

Emerging and lightweight solutions

In addition to the above three major frameworks, many alternatives for performance optimization have emerged in recent years:

How to choose?

When choosing a framework, it is generally recommended to consider the following benchmarks:

• Project size:Angular or React is preferred for large enterprise projects; Vue or Svelte is recommended for small and medium-sized projects or rapid prototyping.
• Team experience:If the team is familiar with HTML templates, Vue is easier to get started; if you prefer strong typing and architecture, Angular is a good choice.
• Maintainability:The communities of React and Vue are strong, making it most convenient to seek support from third-party packages in the future.

Single-page application solutions for Python

In the Python ecosystem, SPA (Single Page Application) development solutions are mainly divided into two categories: one uses Python as a back-end API, and the other uses a specific framework that allows developers to automatically generate a front-end interface with SPA features by simply writing Python code.

1. Data Science and Rapid Prototyping (UI-as-Code)

These frameworks are the most popular because they do not require developers to have HTML/CSS/JS knowledge to develop instantly interactive single-page web pages.

• Streamlit：The current mainstream in data science. It executes the script from top to bottom, and any parameter changes will trigger local updates. Suitable for quickly creating data dashboards.
• Gradio：Specifically designed for machine learning model display. The interface has a high degree of componentization and is particularly good at handling the interaction between image, voice input and model output.
• Dash (by Plotly)：Based on Flask and React. Dash is the most powerful tool for enterprise-level data applications that require highly customized and complex charts.

2. Full-end web application (Modern Full-stack)

This type of framework attempts to challenge the traditional React/Vue + FastAPI model and make full-end development more unified.

3. Traditional backend API solution (Decoupled Architecture)

This is the most standard commercial software development model. Python is only responsible for logic and data, and the front-end is left to the professional JavaScript framework.

// Architecture diagram
Backend (Python): FastAPI / Django Ninja / Flask
Transport protocol: RESTful API or WebSocket
Front-end (JavaScript): Vue.js / React / Svelte (responsible for rendering SPA)

4. HTMX solution (minimalist SPA experience)

This is a very popular trend in recent years. HTMX allows traditional Python web frameworks (such as Django or Flask) to achieve the effect of AJAX partial page update without writing complex JavaScript.

# Django + HTMX example (partial update button)
# After clicking, only the #result area will be replaced and the web page will not be refreshed.
<button hx-post="/get-data/" hx-target="#result">
    Click me to get data
</button>
<div id="result">Waiting...</div>

Select suggestions

• If you are a data scientist:chooseStreamlitorGradio。
• If you want to develop beautiful web pages in pure Python:chooseReflex。
• If you pursue ultimate performance and cross-platform:chooseFlet。
• If you want to upgrade your traditional website in the easiest way:chooseHTMX。

Single-page web development solutions beyond JavaScript and Python

1. Modern HTML enhancement solution (HTMX / Alpine.js)

The core concept of this type of solution is "return to HTML". They advocate that there is no need to write complex JavaScript frameworks to achieve the dynamic effects of SPA.

• HTMX：Send AJAX requests directly through HTML attributes and replace partial content. It lets backends (regardless of language) directly return HTML fragments instead of JSON.
• Alpine.js：Known as the "Tailwind CSS for the web". Write simple logic directly in HTML tags, perfect for static pages that require little interaction.

2. WebAssembly (Wasm) solution

WebAssembly allows developers to write browser-side logic using high-performance languages ​​such as C++, Rust or Go, breaking the monopoly of JavaScript.

3. Static Site Generation (SSG)

This type of solution generates all pages into static HTML files at "build time", which loads very quickly and is very SEO-friendly.

• Astro：Modern SSG representatives adopt the "archipelago architecture" and only load JS in the parts that require interaction.
• Eleventy (11ty)：Minimalist and flexible, it supports multiple template languages.

4. Cross-platform UI solution (Flutter for Web)

The solution launched by Google uses Dart language. It does not use the standard HTML/CSS rendering path, but draws the entire interface through Canvas.

// Flutter logic example
void main() {
  runApp(const MyApp());
}
// The interface is completely drawn by Canvas, which is suitable for transplanting apps with high visual consistency.

5. Low-code / No-code

For internal enterprise tools or quick launch requirements, SPA can be created without handwriting coding.

• Appsmith / Budibase：Quickly create a management backend by dragging components and connecting to the database.
• Webflow：Provides a visual interface for designers to directly produce high-quality web pages.

Solution comparison summary

Self-encapsulated web application

Basic introduction

Traditional web architectures such as PHP + JavaScript are commonly used in server-side deployments, but cannot effectively prevent source code from being accessed or copied, so they are not suitable for commercial licensing and deployment in untrusted environments. To solve this problem, the "Self-hosted Web Application" architecture emerged. It compiles the back-end logic into an unreadable executable file and has built-in HTTP service capabilities, allowing the front-end to still interact with HTML/JS, while the back-end can implement encryption, security, authorization control and other requirements.

advantage

• The back-end program can be encapsulated into an unreadable executable file (binary) to protect the source code.
• License management system can be integrated to prevent unauthorized use.
• Can be deployed across platforms as a local service or desktop application.
• The front-end is still developed using standard web technologies, with low learning costs.

shortcoming

• The development architecture is relatively complex and needs to deal with front-end and back-end communication, authorization and update mechanisms.
• You must design your own deployment and user installation processes.
• Some tools have low desktop integration and require additional UX processing.

Applicable situations

• Internal tools or commercial applications for client deployment need to be provided.
• Source code must be protected from decompilation or theft.
• Restrictions such as authorization management, execution times or time control are required.

Technology comparison table (sorted by market share/usage rate)

Remark

• Market share ranking is estimated based on GitHub usage, enterprise adoption rate, and developer community activity.
• Recommended by C# users: ASP.NET Core and Blazor are the first choices, along with Kestrel’s self-built Web Server.
• If the front-end is completed, the above tools can be used to wrap the back-end service into binary and add an authorization mechanism.

ASP.NET Core

Introduction

ASP.NET Core is a cross-platform, open source, high-performance web application framework developed by Microsoft and supports Windows, Linux and macOS. It is part of the .NET platform and is designed for modern Web APIs, Web Apps, and Microservices. Compared with traditional ASP.NET, the Core version is more lightweight, modular, and can be compiled into an independent executable file (.exe), which is very suitable for self-encapsulated web application architecture.

feature

• Cross-platform support (Windows/Linux/macOS)
• High performance, low memory usage
• Can be compiled into a stand-alone executable file (Self-contained .exe/.dll)
• Built-in Web Server (Kestrel), can be deployed independently
• Can integrate Razor Pages, Blazor, MVC, gRPC and other architectures
• Supports the middleware mechanism to facilitate function expansion
• Good security, supports HTTPS, JWT, OAuth and other verification methods

Advantages for self-encapsulating web applications

• Can be executed directly using Kestrel Web Server without IIS
• The backend can be packaged as .exe or .dll and is not easily decompiled
• Can have built-in authorization mechanism (such as serial number, authorization verification)
• Use with front-end HTML/JS or Blazor to quickly create a Web UI
• Convenient for version control, automatic updates and error tracking

Common packaging patterns

• rear end:Use ASP.NET Core Web API to compile into a stand-alone executable file
• front end:Available in HTML/JS or Blazor framework, embedded in the project or stored externally
• deploy:Produce a single folder (including executable files and static files) for local execution by the client

Authorization management integration method

• Use JWT with serial number/Token mechanism
• Hardware binding (binding MAC, CPU ID, UUID, etc.)
• Connect to License Server for authorization verification
• Local authorization file (encrypted authorization information)

Generate executable file (Self-contained build)

dotnet publish -c Release -r win-x64 --self-contained true -p:PublishSingleFile=true

This command can compile the ASP.NET Core application into a stand-alone executable file (such as `MyApp.exe`), which can be executed directly on the target system without installing .NET Runtime.

Suitable for application scenarios

• Web tools that need to be deployed on the client or packaged into desktop applications
• Commercial software systems require authorization control and source code protection
• Internal enterprise applications, avoiding dependence on IIS or cloud deployment

ASP.NET Core vs. .NET MAUI + Blazor

position

• ASP.NET Core: Cross-platform server-side development framework for building web applications and APIs.
• .NET MAUI + Blazor: Combining .NET MAUI’s cross-platform native applications with Blazor’s Web UI technology, allowing developers to reuse Web UI components on desktop or mobile devices.

Support platform

• ASP.NET Core: Deployed on servers on Windows, Linux, and macOS, providing access through browsers or APIs.
• .NET MAUI + Blazor: Can be executed on Android, iOS, Windows, macOS, and Blazor components are embedded in MAUI applications.

development mode

• ASP.NET Core: Backend Logic + Razor Pages / MVC / Blazor Server / Blazor WASM.
• .NET MAUI + Blazor: Native Application Framework (MAUI) + embed Blazor UI using BlazorWebView controls.

UI rendering

• ASP.NET Core: The UI relies on the browser and is rendered using HTML, CSS, and JS.
• .NET MAUI + Blazor: The UI is displayed in the native application, and the Blazor part renders Razor components through the built-in WebView.

Applicable scenarios

• ASP.NET Core:Build cloud services, internal enterprise systems, web applications and APIs.
• .NET MAUI + Blazor: When you already have a Blazor component or Web UI and want to quickly port it to desktop and mobile devices across platforms.

Integration

ASP.NET Core can be used as the backend of .NET MAUI + Blazor to provide data and API.
If you already have a Blazor Web project, you can move it to a MAUI app almost painlessly and reuse a lot of code.

Summarize

ASP.NET Core focuses on backend and web architecture, and is suitable for developing cloud and API.
.NET MAUI + Blazor focuses on user-side cross-platform applications and is especially suitable for teams that already have Blazor front-end technology stack.
When the two are combined, a complete solution of "back-end service + front-end cross-platform app" can be achieved.

Commonly used IDEs for ASP.NET Core development

Visual Studio

• Developed by Microsoft, it is the optimal IDE for developing ASP.NET Core
• Supports Windows only (some features are Windows only)
• Supports all .NET development functions such as Razor, Blazor, Web API, EF Core, etc.
• Graphic design, advanced debugging, unit testing, NuGet, and publishing tools are all available.
• Can integrate Azure, Docker, Git and other development services
• Recommended version:Visual Studio 2022 and above
• Version selection:
  • Community(Free, suitable for individuals and small development teams)
  • Professional / Enterprise(Paid, enterprise-grade support and features)

Visual Studio Code

• Cross-platform (Windows, Linux, macOS)
• Lightweight editor, you need to install the C# extension kit yourself (provided by OmniSharp)
• Supports ASP.NET Core development such as Razor, Blazor, Web API, EF Core, etc.
• Need to manually set launch.json and tasks.json for debugging and compilation
• Suitable for developers to customize development environment and tool chain
• Free and open source

JetBrains Rider

• Developed by JetBrains, cross-platform (Windows, Linux, macOS)
• Supports ASP.NET Core, Blazor, Razor, Web API, EF Core, etc.
• Integrated ReSharper analysis tool, powerful IntelliSense and reconstruction functions
• Support Docker, Git, CI/CD tool chain
• There is a fee, but the cost is lower than Visual Studio Enterprise

Summary comparison table

Create an ASP.NET Core project in VS Code

Preparation

1. Install.NET SDK: Go to.NET official download page, download and install the latest version.
2. InstallVisual Studio Code。
3. Install in VS CodeC# Extension Kit(provided by Microsoft).

Create project

1. Open the integrated terminal of VS Code (shortcut key:Ctrl + `)。
2. Enter the following commands to create an ASP.NET Core project:

   dotnet new webapp -o MyAspNetApp

   • webapp: Build ASP.NET Core web applications with Razor Pages.
   • -o MyAspNetApp:Specify the name of the project folder.
3. Enter the project folder:

   cd MyAspNetApp

Execution project

1. Enter in the terminal:

   dotnet run

2. By default it will be inhttps://localhost:5001orhttp://localhost:5000implement.

Open the project in VS Code

1. chooseFile → Open folder, load the newly createdMyAspNetApp。
2. When installing the necessary NuGet packages, use:

   dotnet add package package name

Common project types

• dotnet new webapp → Razor Pages Web App
• dotnet new mvc→ MVC architecture
• dotnet new webapi→ Web API Project

VS Code debugging ASP.NET Core project settings

Create debugging profile

1. Open the project folder in VS Code.
2. according toCtrl + Shift + P, enter and selectDebug: Open launch.json。
3. choose.NET Coreenvironment, will be automatically generated.vscode/launch.json。

Example launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": ".NET Core Launch (web)",
      "type": "coreclr",
      "request": "launch",
      "preLaunchTask": "build",
      "program": "${workspaceFolder}/bin/Debug/net8.0/MyAspNetApp.dll",
      "args": [],
      "cwd": "${workspaceFolder}",
      "stopAtEntry": false,
      "serverReadyAction": {
        "action": "openExternally",
        "pattern": "\\bNow listening on:\\s+(https?://\\S+)"
      },
      "env": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      },
      "sourceFileMap": {
        "/Views": "${workspaceFolder}/Views"
      }
    }
  ]
}

Create build settings

1. VS Code will also.vscodeFolder generationtasks.json。
2. If not, you can add a new construction job:

   {
     "version": "2.0.0",
     "tasks": [
       {
         "label": "build",
         "command": "dotnet",
         "type": "process",
         "args": [
           "build",
           "${workspaceFolder}/MyAspNetApp.csproj"
         ],
         "problemMatcher": "$msCompile"
       }
     ]
   }
   

Execution and debugging

1. according toF5Or select from the "Execution and Debug" panel on the left.NET Core Launch (web)。
2. VS Code will automatically build and start the ASP.NET Core project and open it in the browserhttps://localhost:5001。
3. Breakpoints can be set in C# programs for real-time debugging.

VS Code debugging ASP.NET Core Web API project settings

Create a Web API project

1. Enter in the terminal:

   dotnet new webapi -o MyWebApiApp
   cd MyWebApiApp
   code .
   

2. This will create a Web API project and open it in VS Code.

Setting launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": ".NET Core Launch (web API)",
      "type": "coreclr",
      "request": "launch",
      "preLaunchTask": "build",
      "program": "${workspaceFolder}/bin/Debug/net8.0/MyWebApiApp.dll",
      "args": [],
      "cwd": "${workspaceFolder}",
      "stopAtEntry": false,
      "serverReadyAction": {
        "action": "openExternally",
        "pattern": "\\bNow listening on:\\s+(https?://\\S+)"
      },
      "env": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      },
      "sourceFileMap": {
        "/Views": "${workspaceFolder}/Views"
      }
    }
  ]
}

Set tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "build",
      "command": "dotnet",
      "type": "process",
      "args": [
        "build",
        "${workspaceFolder}/MyWebApiApp.csproj"
      ],
      "problemMatcher": "$msCompile"
    }
  ]
}

Execution and testing API

1. according toF5Or select from the Execution and Debug panel.NET Core Launch (web API)。
2. After startup, the server willhttps://localhost:5001orhttp://localhost:5000。
3. availableSwagger UI(Project default) Test the API in the browser.
4. You can also test the API using Postman or the REST Client plugin for VS Code.

Create a REST Client test sample file

Install the REST Client extension

1. Search the VS Code Extension StoreREST Client。
2. Ready to use after installation.httpor.restArchive testing API.

Add test.http file

### Test GET API
GET https://localhost:5001/weatherforecast
Accept: application/json

###

### Test POST API example
POST https://localhost:5001/api/sample
Content-Type: application/json

{
  "id": 1,
  "name": "Test data"
}

Usage

1. Create in the project root directorytest.http。
2. Once you open the archive, above each request you will seeSend Requestbutton.
3. Click to send an API request directly in VS Code and view the response.

Kestrel

Introduction

Kestrel isASP.NET CoreA built-in cross-platform web server developed by Microsoft. It is designed with high performance and lightweight, supports HTTP/1.1 and HTTP/2, and is the default server for ASP.NET Core applications. Using Kestrel allows developers to directly wrap web applications asself-packaging executable file, you can start and provide HTTP services locally without relying on external servers such as IIS, Apache or Nginx.

feature

• Cross-platform support (Windows, Linux, macOS)
• Native support for HTTPS, HTTP/2, WebSocket and other protocols
• High performance, suitable for embedded or self-packaging applications
• Internal service or standalone server that can act as a reverse proxy
• Can be executed directly without installing additional server software

Kestrel and self-encapsulated web applications

• Kestrel is available asNative HTTP API provider, used with front-end UI
• Suitable for use with ASP.NET Core to compile the entire application into an independent execution file (.exe)
• Authorization and verification logic can be integrated as the security foundation of web applications.
• permeableUseUrlsSet the local port and path of the service

Simple sample code

public class Program
{
    public static void Main(string[] args)
    {
        var builder = WebApplication.CreateBuilder(args);

        builder.WebHost.UseKestrel()
                       .UseUrls("http://localhost:5000");

        var app = builder.Build();

        app.MapGet("/", () => "Hello from Kestrel!");
        app.Run();
    }
}

Deployment method

• usedotnet publishPackage the application with Kestrel into a single executable
• No external Web Server is required and can be started directly on the target machine
• Can be packaged and deployed with front-ends such as Blazor or HTML/JS

Differences from IIS/Nginx

Applicable situations

• Applications that need to be packaged as native Web Apps
• Want to deploy to different platforms without relying on external servers
• Commercial applications that need to integrate license verification and API

ASP.NET Core is packaged and deployed together with the front-end (HTML/JavaScript)

Introduction

ASP.NET Core supports integrating front-end resources (HTML, CSS, JavaScript, SPA, etc.) and back-end API services into a single application and deploying it as an independent execution unit (Self-contained application) to achieve the goals of simple deployment, source code protection and license control.

Common front-end integration methods

• Static Files:Put HTML/CSS/JS inwwwroot/A folder for ASP.NET Core to serve as static resources.
• Front-end and back-end separation SPA (React/Vue/Angular):After building the front-end project (built using tools such as Webpack/Vite) into static resources, copy it towwwroot/。
• Razor Pages / Blazor Server：Use the UI framework provided by ASP.NET Core to write pages directly (not pure HTML/JS, but tightly integrated with front-end logic).

Deployment steps example

1. Create an ASP.NET Core project (optional Web API + static website or Blazor)
2. Put the front-end build results intowwwroot,For example:
   • Vue：npm run buildlaterdist/Copy intowwwroot/
   • React：npm run buildlaterbuild/Copy intowwwroot/
3. confirmProgram.csStatic file service is enabled in:

   app.UseStaticFiles();

4. Set the catch-all route to support SPA (if Vue/React):

   
   app.MapFallbackToFile("index.html");
       

5. Deploy the application using:
   • Generate executable file (Self-contained):
     dotnet publish -c Release -r win-x64 --self-contained
   • Generate Docker image files (can be deployed across platforms)
   • Deploy to IIS, Nginx, Kestrel, or cloud platforms (Azure, AWS, GCP)

advantage

• Integrated deployment of front-end and back-end to simplify maintenance process
• Can be packaged into a single executable file to facilitate distribution and protection of source code
• Support license control and offline deployment
• Integrate the .NET ecosystem and support EF Core, Identity, security verification, etc.

shortcoming

• If you use Razor/Blazor, there is a learning threshold for those who are not familiar with .NET.
• The front-end needs to be compiled and integrated, and the development process is complicated.
• Larger size after packaging (especially self-contained mode)

ASP.NET Core MVC

What is ASP.NET Core MVC

ASP.NET Core MVC is a cross-platform web application framework launched by Microsoft. It is based on the Model-View-Controller (model-view-controller) design pattern and provides a structured and modular way to develop dynamic websites and Web APIs.

Main features

• Separation of Concerns: Model is responsible for data and logic, View is responsible for UI presentation, and Controller is responsible for request processing.
• Supports routing system and can flexibly define URL rules
• Built-in Strongly Typed View support for easy binding to Model
• Supports dependency injection (Dependency Injection) to facilitate testing and expansion
• Can be used to build RESTful APIs and dynamic web pages
• Cross-platform support for Windows, Linux, macOS

basic structure

• Model: Represents data structure and business logic
• View: Generate HTML UI using Razor syntax
• Controller: Process user requests and return views or data

Simple example

// Model
public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

//Controller
public class ProductsController : Controller
{
    public IActionResult Index()
    {
        var products = new List<Product>
        {
            new Product { Id = 1, Name = "laptop", Price = 29999 },
            new Product { Id = 2, Name = "Mouse", Price = 499 },
            new Product { Id = 3, Name = "Keyboard", Price = 899 }
        };

        return View(products);
    }
}

// View (Index.cshtml)
@model List<Product>

<table border="1" cellpadding="6" cellspacing="0">
    <thead>
        <tr>
            <th>Number</th>
            <th>Name</th>
            <th>Price</th>
        </tr>
    </thead>
    <tbody>
        @foreach(var item in Model)
        {
            <tr>
                <td>@item.Id</td>
                <td>@item.Name</td>
                <td>@item.Price.ToString("C")</td>
            </tr>
        }
    </tbody>
</table>

ASP.NET Core display table

Sample code

<!-- Product.cs - Data Model -->
public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

<!-- ProductsController.cs - Controller (ASP.NET Core MVC) -->
public class ProductsController : Controller
{
    public IActionResult Index()
    {
        var products = new List<Product>
        {
            new Product { Id = 1, Name = "laptop", Price = 29999 },
            new Product { Id = 2, Name = "Mouse", Price = 499 },
            new Product { Id = 3, Name = "Keyboard", Price = 899 }
        };

        return View(products);
    }
}

<!-- Views/Products/Index.cshtml - Razor View page -->
@model List<Product>

<table border="1" cellpadding="6" cellspacing="0">
    <thead>
        <tr>
            <th>Number</th>
            <th>Name</th>
            <th>Price</th>
        </tr>
    </thead>
    <tbody>
        @foreach (var item in Model)
        {
            <tr>
                <td>@item.Id</td>
                <td>@item.Name</td>
                <td>@item.Price.ToString("C")</td>
            </tr>
        }
    </tbody>
</table>

Razor

What is Razor

Razor is a markup language developed by Microsoft for ASP.NET Core that allows developers to embed C# code in HTML pages. It combines standard HTML and C# to make dynamically generating web pages simple and intuitive.

feature

• Concise syntax, easy to write and read
• Support server-side rendering
• Tight integration with ASP.NET Core MVC or Razor Pages
• You can directly use C# language features, such as conditional judgment, loops, function calls, etc.
• High performance after compilation, suitable for large and medium-sized web application development

Usage scenarios

• ASP.NET Core MVC View page
• Dynamic pages for Razor Pages
• Web applications that mix static and dynamic content

example

@page
@model IndexModel

<h1>Welcome to the Razor page</h1>

<p>Today’s date: @DateTime.Now.ToString("yyyy-MM-dd")</p>

@if(Model.Items != null && Model.Items.Any())
{
    <ul>
    @foreach(var item in Model.Items)
    {
        <li>@item</li>
    }
    </ul>
}
else
{
    <p>No data displayed</p>
}

Reasons and solutions for NullReferenceException in Razor @foreach

Problem description

Use in Razor View:

@foreach(var item in Model)
{
    <div>@item</div>
}

If the following error occurs:

System.NullReferenceException: Object reference not set to an instance of an object.

expressModelfornull, resulting in the inability to loop.

Common causes

• The controller does not pass the Model to the View.
• The Model object passed is null.
• Model is not of type IEnumerable or List.

Solution

1. Make sure you pass the correct Model in the controller, for example:

public IActionResult Index()
{
    var data = new List<string> { "A", "B", "C" };
    return View(data);
}

2. Declare the Model type above the Razor View file:

@model IEnumerable<string>

3. Check whether the Model is null and then execute the loop:

@if (Model != null)
{
    foreach (var item in Model)
    {
        <div>@item</div>
    }
}
else
{
    <div>No data</div>
}

suggestion

Best practice isMake sure the Model must have a value in the controller(even an empty collection) to avoid View handling null situations. For example:

return View(data ?? new List<string>());

MVC has two correct ways to use Controller

Basic concepts

In ASP.NET Core MVC, a project can have multiple Controllers, each Controller is responsible for different functions or areas. For example:

• HomeController— Processing homepage and static pages
• ProductController— Handle product management

Create multiple Controllers

Every Controller must inheritControllercategory and stored inControllersfolder.

// HomeController.cs
public class HomeController : Controller
{
    public IActionResult Index()
    {
        return View();
    }
}

// ProductController.cs
public class ProductController : Controller
{
    public IActionResult List()
    {
        var products = new List<string> { "Computer", "Mobile phone", "Tablet" };
        return View(products);
    }
}

Corresponding Views

MVC's View will create folders based on the Controller name by default, for example:

• Views/Home/Index.cshtml
• Views/Product/List.cshtml

Call Actions of different Controllers in View

Can be usedasp-controllerandasp-actionTag Helpers:

<a asp-controller="Home" asp-action="Index">Back to homepage</a>
<a asp-controller="Product" asp-action="List">Product List</a>

Routing settings

existProgram.csorStartup.cs, the default route is usually:

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

This means that if the URL is/, will automatically guideHomeController.Index(). If the URL is/Product/List, it will be executedProductController.List()。

in conclusion

You can have multiple Controllers at the same time in MVC as long as:

1. Each Controller inheritsController
2. existViewsCreate corresponding folders and files in
3. throughasp-controllerandasp-actionCorrect call
4. Confirm routing settings are correct

How to use multiple Controllers for the same View

key concepts

• Razor View itself only binds oneModel(or a composite ViewModel), but can display or link to data/Actions from multiple Controllers on the same page.
• Common methods: merge data into a single ViewModel, Partial View / ViewComponent, or call other Controllers through AJAX.

Method 1: Combine data into a ViewModel in the Controller (recommended)

// Models/ViewModels.cs
public class HomePageViewModel {
    public IEnumerable<Product> Products { get; set; }
    public IEnumerable<Order> RecentOrders { get; set; }
}

// HomeController.cs
public IActionResult Index() {
    var vm = new HomePageViewModel {
        Products = productService.GetTopProducts(),
        RecentOrders = orderService.GetRecentOrders()
    };
    return View(vm);
}

// Views/Home/Index.cshtml
@model HomePageViewModel

<h2>Product</h2>
@foreach(var p in Model.Products){ <div>@p.Name</div> }

<h2>Recent Orders</h2>
@foreach(var o in Model.RecentOrders){ <div>@o.Id</div> }

Method 2: Partial View (each Controller provides data, and then the parent Controller combines or calls Partial)

// Views/Product/_ProductList.cshtml (partial)
@model IEnumerable<Product>
@foreach(var p in Model){ <div>@p.Name</div> }

// Views/Home/Index.cshtml (parent View)
@model HomePageViewModel
<div>
  @Html.Partial("_ProductList", Model.Products)
</div>

Method three: ViewComponent (equivalent to a reusable small Controller + View)

// Components/ProductListViewComponent.cs
public class ProductListViewComponent : ViewComponent {
    private readonly IProductService _svc;
    public ProductListViewComponent(IProductService svc){ _svc = svc; }
    public IViewComponentResult Invoke(int count) {
        var products = _svc.GetTopProducts(count);
        return View(products); // Views/Shared/Components/ProductList/Default.cshtml
    }
}

// used in Razor
@await Component.InvokeAsync("ProductList", new { count = 5 })

Method 4: Front-end AJAX provides APIs from different Controllers (suitable for dynamic loading)

<!-- Views/Home/Index.cshtml -->
<div id="product-area">Loading...</div>

<script>
fetch('/api/product/top5')
  .then(r => r.json())
  .then(data => {
    document.getElementById('product-area').innerHTML =
      data.map(p => `
${p.name}
`).join('');
  });
</script>

Method 5: Put multiple links to different Controllers in the View (the simplest navigation)

<a asp-controller="Product" asp-action="List">Product List</a>
<a asp-controller="Order" asp-action="History">Order History</a>

Select suggestions

• If you need to display multiple data sources simultaneously on the same page: use synthesisViewModelorViewComponent(more modular).
• To reuse or render blocks individually: usePartial VieworViewComponent。
• If you need asynchronous or on-demand loading: use AJAX to get data from different Controller's APIs.
• Avoid directly calling other Controller actions in View to obtain data (the Controller/Service layer should be responsible for obtaining data) to maintain separation of responsibilities and testability.

web old technology

Java Applet

Basic concepts

A Java Applet is a small application written in the Java language that can be executed through a web browser and embedded into an HTML page. It was first widely used in the 1990s to create interactive web pages, such as animations, games, and chart visualizations.

Execution method

Applet must be executed on a browser that supports Java Plugin, through<applet>or<object>Tags are embedded in HTML and are loaded and executed by the user-side JVM (Java Virtual Machine).

security restrictions

Since Applets can be executed on the client side, in order to prevent malicious behavior, the execution environment adopts a "sandbox mechanism" for security isolation, such as prohibiting access to the local file system or execution of external programs.

Support situation and current situation

• Google Chrome: NPAPI support has been completely removed since 2015, and Java Applets are no longer supported.
• Mozilla Firefox: Officially stopped supporting NPAPI plug-ins in 2017.
• Microsoft Edge: Java Applets have not been supported since launch.
• Safari: Java Applet execution support has been completely removed starting with macOS Catalina.

Oracle Official Policy

Oracle has announced the removal of Applet API since Java 9, and will completely abolish Applet in Java 11. Java Web Start, another desktop execution technology, is also out of maintenance.

alternatives

• JavaFX：Provides a more modern GUI framework and Web integration capabilities, but does not have built-in browser support.
• HTML5 + JavaScript：Becoming a mainstream alternative technology, supporting cross-platform and higher interactivity.
• WebAssembly：Other languages ​​can be compiled into a browser executable format, making them a potential choice for high-performance computing.

Summarize

Java Applets have entered the phase of elimination, and modern web development trends tend to use open standard technologies such as HTML5, JavaScript and WebAssembly. Developers should avoid using applets and move existing applications to modern technology platforms.

Java Applet Example

The following is an example Java Applet that displays a simple message:

HTML code

<!DOCTYPE html>
<html lang="zh-Hant">
<head>
<meta charset="UTF-8">
<title>Java Applet Example</title>
</head>
<body>
<h1>Java Applet Example</h1>
<applet code="HelloWorldApplet.class" width="300" height="300>
    <param name="message" value="Hello, world! ">
    Your browser does not support Java Applets.
</applet>
</body>
</html>

Java Applet code

import java.applet.Applet;
import java.awt.Graphics;

public class HelloWorldApplet extends Applet {
String message;

public void init() {
    message = getParameter("message");
}

public void paint(Graphics g) {
    g.drawString(message, 20, 20);
}
}

Compile and execute

1. Save the Java code asHelloWorldApplet.java, and execute it in the command linejavac HelloWorldApplet.javato compile.

2. Make sure the generated.classThe file is in the same directory as the HTML file.

3. Use an environment that supports Java Applets to execute the HTML file.

Things to note

Since most modern browsers no longer support Java Applets, it is recommended to consider using other technologies (such as JavaFX or web applications) to achieve similar functionality.

email: [email protected]

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