3v4l.org

run code in 300+ PHP versions simultaneously
<?php class Foo { public $clbk; public function __construct($b = false) { $f = new self(); if($b) { $this->clbk = function() use ($f) { return $f; }; } } } $f = new Foo(true); var_dump($f->clbk());

preferences:
42.6 ms | 402 KiB | 5 Q