本文档中使用的伪类型

mixed

mixed 说明一个参数可以接受多种不同的（但并不必须是所有的）类型。

例如 gettype() 可以接受所有的 PHP 类型，str_replace() 可以接受字符串和数组。

number

number 说明一个参数可以是 integer 或者 float。

callback

有些诸如 call_user_function() 或 usort() 的函数接受用户自定义的函数作为一个参数。Callback 函数不仅可以是一个简单的函数，它还可以是一个对象的方法，包括静态类的方法。

一个 PHP 函数用函数名字符串来传递。可以传递任何内置的或者用户自定义的函数，除了 array()，echo()，empty()，eval()，exit()，isset()，list()，print() 和 unset()。

一个对象的方法以数组的形式来传递，数组的下标 0 指明对象名，下标 1 指明方法名。

对于没有实例化为对象的静态类，要传递其方法，将数组 0 下标指明的对象名换成该类的名称即可。

例 11-13. Callback 函数实例


<?php
// 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'));
?>

add a note User Contributed Notes

Hayley Watson
24-May-2007 05:44


The mixed pseudotype is explained as meaning "multiple but not necessarily all" types, and the example of str_replace(mixed, mixed, mixed) is given where "mixed" means "string or array".

Keep in mind that this refers to the types of the function's arguments _after_ any type juggling.

levi at alliancesoftware dot com dot au
08-Feb-2007 10:44


Parent methods for callbacks should be called 'parent::method', so if you wish to call a non-static parent method via a callback, you should use a callback of

<?

 // always works

 $callback = array($this, 'parent::method') 



 // works but gives an error in PHP5 with E_STRICT if the parent method is not static

 $callback array('parent', 'method'); 

?>

Edward
01-Feb-2007 10:15


To recap mr dot lilov at gmail dot com's comment: If you want to pass a function as an argument to another function, for example "array_map", do this:



regular functions: 

<? 

array_map(intval, $array)

?>



static functions in a class:

<?

array_map(array('MyClass', 'MyFunction'), $array)

?>



functions from an object:

<?

array_map(array($this, 'MyFunction'), $array)

?>



I hope this clarifies things a little bit

mr dot lilov at gmail dot com
12-Aug-2005 01:17


This's a useful example about callback, Look at the session_set_save_handler function.



From: http://www.zend.com/zend/spotlight/code-gallery-wade8.php



<?php 



/* Create new object of class */ 

$ses_class = new session(); 



/* Change the save_handler to use the class functions */ 

session_set_save_handler (array(&$ses_class, '_open'), 

                          array(&$ses_class, '_close'), 

                          array(&$ses_class, '_read'), 

                          array(&$ses_class, '_write'), 

                          array(&$ses_class, '_destroy'), 

                          array(&$ses_class, '_gc')); 



/* Start the session */ 

session_start(); 



class session 

{ 

    /* Define the mysql table you wish to use with 

       this class, this table MUST exist. */ 

    var $ses_table = "sessions"; 



    /* Change to 'Y' if you want to connect to a db in 

       the _open function */ 

    var $db_con = "Y"; 



    /* Configure the info to connect to MySQL, only required 

       if $db_con is set to 'Y' */ 

    var $db_host = "localhost"; 

    var $db_user = "username"; 

    var $db_pass = "password"; 

    var $db_dbase = "dbname"; 



    /* Create a connection to a database */ 

    function db_connect() { 

    ............

    } 



    /* Open session, if you have your own db connection 

       code, put it in here! */ 

    function _open($path, $name) {

    .............

    } 



    /* Close session */ 

    function _close() { 

    ..............

    } 



    /* Read session data from database */ 

    function _read($ses_id) { 

    .................

    } 



    /* Write new data to database */ 

    function _write($ses_id, $data) { 

    ...........

    } 



    /* Garbage collection, deletes old sessions */ 

    function _gc($life) { 

    ............

    } 

} 

?>

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