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<?php $dupa = function($dupa) { return $dupa; }; $dupa = $dupa($dupa); var_dump($dupa);
based on hbSAi
Output for 5.3.12 - 7.2.0
object(Closure)#1 (1) { ["parameter"]=> array(1) { ["$dupa"]=> string(10) "<required>" } }