Re: Possible RFC: UniqueInterface that throws exception at refcount > 1

> Yes, it would be a dynamic uniqueness system, kind of. > > Another more flexible alternative would be to add magic methods at > refcount = 1 and refcount > 1, possibly __owned() and __shared(int > $refcount), for classes that implement a TrackReferencesInterface or > similar. But this would need to do ~0 performance hit if not used, > don't know if possible. Then again, php already calls __destruct if it exists when the refcount goes to 0, so I may be overestimating the potential performance impact. There's a lot of edge cases - probably way more than I mention here. Running into those edge cases, you might find the feature unsatisfactory if it were to be implemented. For example, - The UniqueReferenceException itself creates a trace, that increments reference counts, which might itself cause a UniqueReferenceException. Workarounds for that would probably involve allowing multiple objects to reference a UniqueInterface, and then it would be a weaker guarantee. - unserialize() keeps extra references to ensure that it can delete the created objects if the original references were overwritten. __wakeup() and __unserialize() - The reference count is incremented when calling __destruct(), I think. ``` <?php class UniqueObject implements UniqueInterface{ public function __construct() { debug_zval_dump($this); // refcount 3 - and then what about $GLOBALS['something'] = $this inside __construct } public function someUtilMethod() { // object(UniqueObject)#1 (0) refcount(2){ // } debug_zval_dump($this); } } // The reference count goes to 2 in someUtilMethod because there's 2 references. // the temporary and $this. (new UniqueObject())->someUtilMethod(); ``` - Tyson