3v4l.org

run code in 300+ PHP versions simultaneously
<?php abstract class Base {} class Sub extends Base {} abstract class Parent { abstract public function foo(Base $x); } class Child extends Parent { public function foo(Child $x) {} }
Output for 5.4.2 - 5.4.45, 5.5.24 - 5.5.30, 5.6.7 - 5.6.14
Fatal error: Cannot use 'Parent' as class name as it is reserved in /in/Q2cfM on line 6
Process exited with code 255.

preferences:
203.85 ms | 1387 KiB | 65 Q