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Last updated: Tue, 19 Sep 2006

CI. Object property and method call overloading


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.


This extension is EXPERIMENTAL. The behaviour of this extension -- including the names of its functions and anything else documented about this extension -- may change without notice in a future release of PHP. Use this extension at your own risk.


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.


No external libraries are needed to build this extension.


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.

The windows version of PHP has built in support for this extension. You do not need to load any additional extension in order to use these functions.

Note: Builtin support for overload is available with PHP 4.3.0.

Runtime Configuration

This extension has no configuration directives defined in php.ini.

Resource Types

This extension has no resource types defined.

Predefined Constants

This extension has no constants defined.


Some simple examples on using the overload() function:

Example 1. Overloading a PHP class


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

$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);


Table of Contents
overload -- Enable property and method call overloading for a class

Last updated: Tue, 19 Sep 2006