Callbacks

Example #1 Callback function examples

<?php

　　//An example callback function

　　function my_callback_function(){

　　echo 'hello world!';

}

class MyClass{

　　static 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'));

//　　Type 4:Static class method call(As of PHP 5.2.3)

call_user_func('MyClass::myCallbackMethod');

//　　Type 5:Relative static class method call(As of PHP 5.3.0)

class A{

　　public static function who(){

　　　　echo "A\n";

　　}

}

class B extends A{

　　public static function who(){

　　　　echo "B\n";

　　}

}

call_user_func(array('B'，'parent::who'));

?>

 

Example #2 Callback example using a Closure

<?php

//Our closure

$double =function($a){

　　return $a*2;

}

//This is our range of numbers

$numbers=range(1,5);

//Use the closure as a callback here to

//double the size of each element in our range

$new_numbers=array_map($double,$numbers);

print implode('  ',$new_numbers);

?>

以上例程会输出：

2 4 6 8 10

Note:In PHP 4,it was necessary to use a reference to create a callback that points

to the actual object,and not a copy of it.

Note:

在函数中注册有多个回调内容时（如使用call_user_func()与call_user_func_array()）,如在前一个回调中有未捕获的异常，其后的将不再被调用。