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[2007-10-11 23:08 UTC] jmaxwilson at sixteensmallstones dot org
Description:
------------
If __call() is used to implement a method in a parent class, and the method is overridden in an inherited child class using a real method declaration that calls parent::methodName(), __call() is never invoked and PHP reports a fatal error saying that the method is undefined.
You can work around the bug by replacing parent::methodName() with parent::__call('methodName',null), but it means that you have to know which of the parent's methods are implemented using __call() in order to override them in a child class.
The child class should be agnostic to whether the parent's methods are real or magic.
This bug was reported in PHP5.1 RC1 (http://bugs.php.net/bug.php?id=34739) but was improperly marked as bogus with the explanation that "__call() is not used when calling static methods." The use of the paamayim-nekudotayim (::) with the parent keyword is not to resolve static scope but to resolve inherited scope for an overridden method, therefore the issue should be reconsidered.
Reproduce code:
---------------
<?php
class A {
function __call($strMethod, $arrArgs) {
return "PHP " .phpversion();
}
}
class B extends A {
function getVersion() {
return parent::getVersion() . " Rocks!";
}
}
$A = new A();
echo $A->getVersion() . "<br/>";
$B = new B();
echo $B->getVersion() . "<br/>";
?>
Expected result:
----------------
PHP 5.2.4
PHP 5.2.4 Rocks!
Actual result:
--------------
PHP 5.2.4
Fatal error: Call to undefined method A::getversion() in C:\www\test.php on line 10
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Last updated: Thu Nov 21 09:01:32 2024 UTC |
This is fixed in 5_3 but you have to define __callstatic like this <?php class A { function __call($strMethod, $arrArgs) { return "PHP " .phpversion(); } static function __callstatic($strMethod, $arrArgs) { return "PHP " .phpversion(); } } class B extends A { function getVersion() { return parent::getVersion() . " Rocks!"; } } $A = new A(); echo $A->getVersion() . "<br/>"; $B = new B(); echo $B->getVersion() . "<br/>"; ?>Thanks for the feedback. However, adding a magic __callstatic() method doesn't actually fix the problem. I think there is some misunderstanding about the scope resolution operator (::). While it is often used to access the static methods of a class, when applied to the keyword "parent" it is used to access the _instance_ methods of a the parent class. So, calling parent::getVersion() is calling the _instance_ method of the parent from the child class, not a static method. Why is this important? What if the method needs to get or set properties of the instance? It must be an instance method. The $this pseudo-variable is not even available within static methods. To illustrate, the example code can be modified like this: <?php class A { var $arrValues = array(); function __construct() { $this->arrValues['PHP'] = "PHP " . phpversion(); } function __call($strMethod, $arrArgs) { return $this->arrValues['PHP']; } } class B extends A { function getVersion() { return parent::getVersion() . " Rocks!"; } } $A = new A(); echo $A->getVersion() . "<br/>"; $B = new B(); echo $B->getVersion() . "<br/>"; ?> It would be incorrect for the engine to call the __callstatic() magic method when a child class calls a parent's method. I hope that is not what 5_3 does.