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 ";
}
}
class B extends A{
public static function who(){
echo "B ";
}
}
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。