How to reuse PHP custom functions?

There are two ways to reuse PHP custom functions: 1. Include function files; 2. Automatically load functions. Inclusion method: Define the function in a separate file and then include the file where needed. Automatic loading method: Use PHP's SPLAutoload mechanism to automatically load custom functions. Example: Format date function, inclusion method: define the function in the functions.php file, and include the file in the main.php file; automatic loading method: define the function in the format_date.php file, in the main.php file Register the autoloading function to automatically load the format_date.php file.

How to reuse PHP custom functions

In large PHP projects, reusing code can significantly improve development efficiency. Custom functions are an effective way to reuse code.

Method 1: Include function file

Define the custom function in a separate file (functions.php), and then add it to the required The location contains this file.

// functions.php
function my_custom_function($arg1, $arg2) {
    // ... 函数逻辑 ...
}

// main.php
require_once 'functions.php';
my_custom_function('foo', 'bar');

Method 2: Automatically load functions

Use PHP’s SPLAutoload mechanism to automatically load custom functions.

// my_custom_function.php
function my_custom_function($arg1, $arg2) {
    // ... 函数逻辑 ...
}

// main.php
spl_autoload_register(function ($class) {
    if (file_exists(__DIR__ . "/functions/$class.php")) {
        require "$class.php";
    }
});

my_custom_function('foo', 'bar');

Practical case

Suppose you need to create a function that formats dates.

Method 1: Include function file

// functions.php
function format_date($date, $format) {
    return date($format, strtotime($date));
}

// main.php
require_once 'functions.php';
$formatted_date = format_date('2023-03-08', 'Y-m-d');
echo $formatted_date; // 输出: 2023-03-08

Method 2: Automatically load function

// format_date.php
function format_date($date, $format) {
    return date($format, strtotime($date));
}

// main.php
spl_autoload_register(function ($class) {
    if (file_exists(__DIR__ . "/functions/$class.php")) {
        require "$class.php";
    }
});

$formatted_date = format_date('2023-03-08', 'Y-m-d');
echo $formatted_date; // 输出: 2023-03-08

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