new overloading feature?

I came across an interesting desire today. I'd like to create a new class instance if an only if a "key" value does not already exist. This key value could be looked up in a database, in an array, etc. The following contrived example shows use of a proposed __new() overload function which would be called BEFORE the constructor, and could chose to return a newly constructed object (by calling __construct()) or to return an already existing object. One could certainly call a function which searched for the key value and only instantiated a new object if the existing one was not found, but this seems cleaner. Thoughts? <?php class X { static $allX = array(); var $val; function __construct($val) { $this->val = $val; X::$allX[] =& $this; } function __new($val) { foreach (X::$allX as $x) { if ($x->val == $val) { return $x; } } return __construct($val); } } $try1 = new X(23); /* would return $allX[0] reference */ $try2 = new X(42); /* woudl return $allX[1] reference */ $try3 = new X(23); /* would return $allX[0] reference */ ?>