Re: Weak Closures

On 21.01.2022 at 11:31, Dominic Grostate wrote: > I'd like to express my interest in a possible feature concerning weak > references. Currently closures created within a class appear to > contain a reference to the object that created it. This is of course > necessary in order for the closure to retain the necessary scope. > However I would like to suggest we have the option for closure to > weakly reference this object so that when the object is garbage > collected, the closure too may be rendered null or invalid > (inspectable). > > Consider the following example: > https://gist.github.com/orolyn/7651e4127759aad1736547490baa1394 > > The idea here is that without unset($sample) the loop would run > forever, because there is a reference to the callback from the object, > and in turn there is a reference to the object from the main stack. > With the unset($sample), the idea is that before the callback is even > called, the reference to the object is destroyed thusly so is the > reference to callback, and since the callback is only referenced now > in a WeakMap, the callback will finally be gone. > > In reality it appears there is a circular reference between the object > and the callback. I don't know if this is a bug or not, because from > what I can find PHP was fixed a long time ago to resolve circular > references. > > However if this is intentional, I would like the option to make the > closure weak for example: > > $c = WeakClosure::fromCallable(function () {}); > $c = Closure::fromCallable(function () {}, true); > > Please let me know your thoughts, because maybe there is a way of > achieving this with PHP as is. If you trigger the garbage collector manually (i.e. call gc_collect_cycles() after unset($callback)), the loop terminates right away. I'm not sure why it doesn't without manually triggering the GC. Christoph