Online PHP editor | output for 8VDoZ

<?php class Hi { protected $message = 'Hello'; public function setMessage(string $message) { $this->message = $message; } public function sayHello() : Hi { var_dump($this->message); return $this; } } class WrapperCat extends Hi { private $realThing; public function __construct(Hi $realThing) // should be a named constructor instead { $this->realThing = $realThing; } public function sayHello() : Hi { var_dump('WrapperCat Meow! '); return $this->realThing->sayHello(); } } class CopyCat extends Hi { public function __construct(Hi $realThing) // should be a named constructor instead { $this->message = & $realThing->message; } public function sayHello() : Hi { var_dump('CopyCat Meow! ' . $this->message); return $this; } } $hi = new Hi; $wrapperCat = new WrapperCat($hi); $copyCat = new CopyCat($hi); $hi->setMessage('Hello'); var_dump(Hi::class); $hi->sayHello()->sayHello(); var_dump(WrapperCat::class); $wrapperCat->sayHello()->sayHello(); var_dump(CopyCat::class); $copyCat->sayHello()->sayHello(); $hi->setMessage('Hi'); var_dump(Hi::class); $hi->sayHello()->sayHello(); var_dump(WrapperCat::class); $wrapperCat->sayHello()->sayHello(); var_dump(CopyCat::class); $copyCat->sayHello()->sayHello();