How to use PHP callback function and precautions, callback function_PHP tutorial

How to use PHP callback function and precautions, callback function

In PHP, some functions such as call_user_function() or usort() accept a user-defined function as a parameter. The Callback function can not only be a simple function, it can also be a method of an object, including methods of static classes.

A PHP function is passed as a function name string. You can pass any built-in or user-defined function, except array(), echo(), empty(), eval(), exit(), isset(), list(), print() and unset() .

The method of an object is passed in the form of an array. The 0 subscript of the array specifies the object name, and the subscript 1 specifies the method name.

For a static class that has not been instantiated as an object, to pass its method, replace the object name specified by the array 0 subscript with the name of the class.

Callback function example:

Copy code The code is as follows:

// An example callback function
function my_callback_function() {
echo 'hello world!';
}
// An example callback method
class MyClass {
function myCallbackMethod() {
echo 'Hello World!';
}
}
// Type 1: Simple callback
call_user_func('my_callback_function');
// Type 2: Static class method call
call_user_func(array('MyClass', 'myCallbackMethod'));
// Type 3: Object method call
$obj = new MyClass();
call_user_func(array($obj, 'myCallbackMethod'));
?>

http://www.phpe.net/manual/language.pseudo-types.php
http://cn.php.net/manual/en/language.pseudo-types.php

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