PHP Object-Caching and Reference Counting

Hello there... I am making my debut appearance here hoping that I am not giving offense to anyones well honed php-instincts or programming practices with my feature-request. This is what it comes down to, I guess. A Feature Request for some meta-info on the instantiated PHP-Objects. Specifically I want to know how many references are currently pointing to any one object. Since PHP's Memory Management is based on Reference-Counting this information should already be available "somewhere". Not knowing any php-source-code internals, I can't even guess at the problems which prohibit the implementation of such a feature. Nevertheless I'd like to point out an advantage to the community if the reference-count were available. I have been working on a large project for 6 years now and I got to a point where I'd like to cache certain objects singleton-like. To better explain my problem I provide this small example which surely is error-prone but should get the basic idea across. <? class MyObject { private static $instances = array(); protected $id; private function __constructor($id){ $this->id = $id; } /** * Returns an instance of the class. * If no object was instantiated with the given $id before, * it will instantiate a new object which will be associated with the given $id. * * It will also check the current memory-usage and if its used up for more than * 80% it will call the collect() method. * * @param int $id * @return MyObject */ public static function getInstance($id){ if ( !isset(self::$instances[$id]) ) { //check the used up memory wether to collect unused objects or not if ( memory_get_usage() > ini_get('memory limit')*0.8 ) self::collect(); self::$instances[$id] = new MyObject($id); } return self::$instances[$id]; } /** * Removes any object from the cache-list which is not referenced anymore. * (safe for the list and the local-reference to it) */ public static function collect(){ foreach( self::$instances as $id => $instance ) { if ( reference_count($instance) < 3 ) unset(self::$instances[$id]); } } } ?> As you can see I boldly used the function reference_count(Object) even though it doesn't exist. This is exactly what I'd need to allow my concept to work. I keep thinking of any other solutions, but up until now, I didn't find any better solution for this problem. Of course I can always ignore the memory usage and hope that it wont hit the limit...but hoping is a rather ethereal and mystic idea which doesn't go well with my preferred down-to-earth 1 plus 1 equals 2 programming. I know that a lot of you may say: Why do need to do that?...and I'd have to think for 3 days and then write for 4 days and would give up. It seems like a nice solution to me and if any of you have an idea as to how I could implement this differently, please feel free to point it out to me. Thanks for reading this far. Lars