How do PHP functions extend?

PHP provides a function extension mechanism that allows developers to create custom functions. Specific steps include: Use the function keyword to create a custom function. Use function_exists() to check whether the function exists and register it if it does not exist. Extend the built-in function parameters to implement a function of the same name with new parameters. Extend an existing function, for example by registering an extension function with modified functionality to colorize print_r output into JSON format.

PHP Function Extension Guide

Introduction

PHP provides flexible functions Extension mechanism that allows developers to create and use custom functions. This article will guide you how to extend PHP functions and provide a practical case.

Create a custom function

Use the function keyword to create a custom function:

function my_custom_function() {
  // 函数主体
}

Register custom Function

To make a custom function available, it needs to be registered in the PHP function table:

function_exists('my_custom_function'); // 检查函数是否存在

If the function does not exist, use function_exists() Register it:

function_exists('my_custom_function', 'my_custom_function_callback');

where my_custom_function_callback is the callback handler for the function.

Extended function parameters

You can extend the parameters of PHP built-in functions by implementing a function with the same name and adding new parameters:

function array_push_with_default($array, $value, $default = null) {
  if (empty($default)) {
    array_push($array, $value);
  } else {
    array_push($array, $default);
  }
}

Practical case: Extend print_r function

We extend the print_r function to colorize JSON output:

function print_r($data) {
  echo '<pre style="color: green;">';
  parent::print_r(json_encode($data));
  echo '

'; }

By registering the extension function, We can use the modified print_r:

function_exists('print_r', 'print_r_colorized');

print_r(['name' => 'John', 'age' => 30]);

This will output a shaded array in JSON format.

The above is the detailed content of How do PHP functions extend?. For more information, please follow other related articles on the PHP Chinese website!