[php-src] Issue #7870: Self-reference is counted as circular reference

Issue: https://github.com/php/php-src/issues/7870 Author: woho ### Description A self-reference is regarded as a circular reference with implications on garbage collection. A real-world usecase where this can be relevant is setting an instance variable to an anonymous function, which is also a kind of self-reference. Such objects need to be garbage-collected by gc_collect_cycles when creating many of them, or memory exhaustion can result. Would it be possible to make the reference counting smarter to avoid this? ```php <?php $sr = new SelfRef; unset($sr); print("End of script\n"); class SelfRef { function __construct() { $this->self_ref = $this; #$this->self_ref = function() { }; } function __destruct() { print("__destruct\n"); } } ``` Resulted in this output: ``` End of script __destruct ``` But I expected this output instead: ``` __destruct End of script ``` ### PHP Version PHP 8.0.14 ### Operating System _No response_