Online PHP editor | refs for h2TW1

<?php declare(strict_types=1); final class Stacker { private array $stack = []; public function push($obj): Stacker { $this->stack[] = $obj; return $this; } public function shift() { return array_shift($this->stack); } public function pop() { return array_pop($this->stack); } } $stack = new Stacker(); $stack->push(1);