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# XCII. Object property and method call overloading

# 简介

The purpose of this extension is to allow overloading of object property access and method calls. Only one function is defined in this extension, overload() which takes the name of the class that should have this functionality enabled. The class named has to define appropriate methods if it wants to have this functionality: __get(), __set() and __call() respectively for getting/setting a property, or calling a method. This way overloading can be selective. Inside these handler functions the overloading is disabled so you can access object properties normally.

警告
本扩展模块是实验性的。本模块的行为，包括其函数的名称以及其它任何关于此模块的文档可能会在没有通知的情况下随 PHP 以后的发布而改变。使用本扩展模块风险自担。

警告
This extension is not a part of PHP 5. PHP 5 supports __get(), __set() and __call() natively. See the Overloading in PHP 5 page for more information.

# 需求

要编译本扩展模块不需要外部库文件。

# 安装

In order to use these functions, you must compile PHP with the --enable-overload option. Starting with PHP 4.3.0 this extension is enabled by default. You can disable overload support with --disable--overload.

PHP 的 Windows 版本已经内置该扩展模块的支持。无需加载任何附加扩展库即可使用这些函数。

> 注: Builtin support for overload is available with PHP 4.3.0.

# 运行时配置

本扩展模块在 `php.ini` 中未定义任何配置选项。

# 资源类型

本扩展模块未定义任何资源类型。

# 预定义常量

本扩展模块未定义任何常量。

# 范例

Some simple examples on using the overload() function:

例子 1. Overloading a PHP class

`<?php
class OO {
var $a = 111;
var $elem = array('b' => 9, 'c' => 42);
// Callback method for getting a property
function __get($prop_name, &$prop_value)
{
if (isset($this->elem[$prop_name])) {
$prop_value = $this->elem[$prop_name];
return true;
} else {
return false;
}
}
// Callback method for setting a property
function __set($prop_name, $prop_value)
{
$this->elem[$prop_name] = $prop_value;
return true;
}
}
// Here we overload the OO object
overload('OO');
$o = new OO;
echo "\$o->a: $o->a\n"; // print: $o->a: 111
echo "\$o->b: $o->b\n"; // print: $o->b: 9
echo "\$o->c: $o->c\n"; // print: $o->c: 42
echo "\$o->d: $o->d\n"; // print: $o->d:
// add a new item to the $elem array in OO
$o->x = 56;
// instantiate stdclass (it is built-in in PHP 4)
// $val is not overloaded!
$val = new stdclass;
$val->prop = 555;
// Set "a" to be an array with the $val object in it
// But __set() will put this in the $elem array
$o->a = array($val);
var_dump($o->a[0]->prop);
?>`

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