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Date: Tue, 02 Aug 2005 16:05:30 +0200
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Subject: Re: [PHP-DEV] Property Overloading RFC
From: ondrej@kmit.sk (=?UTF-8?B?T25kcmVqIEl2YW5pxI0=?=)

Derick Rethans wrote:
> Hello!
> 
> we're finding some problems with property overloading (__get() and 
> __set()). Here is an RFC describing what we'd like to see changed. 
> Please comment on this.
> 
> 
> Introduction:
> PHP currently supports property overloading with the magic functions __get()
> and __set(). Those methods are called when the code "echo $object->a" or
> "$object->a = 42" are executed and the property "a" is not declared in the
> class. The magic methods are responsibly for:
> - checking if the property actually "exists"
> - setting the value or returning the value depending on the action
> 
> Problems:
> 1. There is no way to document the 'virtual' properties with any of the existing
>    documentation tools (such as phpdoc and doxygen)
> 2. There is no way how the magic methods know if a specific 'virtual' property
>    exists or not as those properties are not declared usually - unless you
>    define an array with property names as a class constant (which is not
>    allowed either).
> 3. There is no way for the magic methods to return a meaningfull error when a
>    property doesn't "exist". Of course it is possible to throw an error with
>    "trigger_error" or "throw" in case a property doesn't "exist" in a specific
>    class, but the file and line numbers would not match the actually get/set
>    action. debug_backtrace() can be used to retrieve the correct file and line,
>    but as you have to do this for every class where you want to use setters and
>    getters *and* you have to implement your own error message rendering
>    function this is not really a suitable option either.

what about:

<?php

class GetSet0 {
	function __get($name) {}
	function __set($name, $value) {}
}

class GetSet1 {
	property $x;
	// or virtual $x, ...

}

class GetSet2 {
	property $x { __get, __set }

	function __get($name) {}
	function __set($name, $value) {}

}

class GetSet3 {
	property $x { getMethod, setMethod }

	function getMethod() {}
	function setMethod($value]) {}

}

?>

Features:
1) Easy way to document properties
2) No BC break with code relies on __get, __set

Clases GetSet0, GetSet1 and GetSet2 are equivalent and third class 
GetSet3 use different methods to handle $x property;

There is a nice way to declare reaonly properties

property $x { getMethod }

or

property $x { getMethod, null }

and writeonly propeties :)

property $x { null, setMethod }

If someone touch undeclared property and class don't have __get/__set 
Zend engine can raise exception ... It's good way? I don't know.

-- 
Ondrej Ivanic
(ondrej@kmit.sk)