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run code in 300+ PHP versions simultaneously
<?php class Foo { public function dump(self $baz) { var_dump($baz); } } class Bar extends Foo { public function dump(Foo $baz) { parent::dump($baz); } } (new Foo)->dump(new Bar); (new Bar)->dump(new Bar); (new Bar)->dump(new Foo);

preferences:
34.53 ms | 402 KiB | 5 Q