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# XCII. Object property and method call overloading

# 介紹

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
這個延伸是實驗性質的。這個延伸的行為 -- 包括函數名稱和包含此延伸的任何其它文件 -- 在未來PHP的發行中可能會在不通知的情況改變。使用此延伸需自行承擔風險。

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

建立這個延伸不需要任何外部程式庫。

# 安裝

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.

Windows 版本的 PHP 已內建此延伸的支援﹐所以你毋須再載入附加的延伸來使用這些功能。

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

# 執行時期組態

`php.ini`中沒有定義此延伸的組態指令。

# 資源類型

這個延伸沒有定義任何資源。

# 預先定義常數

這個延伸沒有定義任何常數。

# 範例

Some simple examples on using the overload() function:

範例 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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