LXXIX. Object property and method call
overloading
Introduction
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.
Warning
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.
Requirements
No external libraries are needed to build this extension.
Installation
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.
Examples
Some simple examples on using the overload() function: Example
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:
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);
?>
Warning
As this is an experimental extension, not all things work.
There is no __call() support currently, you can only overload
the get and set operations for properties. You cannot invoke
the original overloading handlers of the class, and __set()
only works to one level of property access.
Table of Contents
overload -- Enable property and method call overloading
for a class
