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run code in 500+ PHP versions simultaneously
<?php class B { protected static $c = 1; } class C1 extends B { function f(B $x) { return $x::$c; } } class C2 extends B { protected static $c = 2; } var_dump((new C1)->f(new C2));

preferences:
46.79 ms | 849 KiB | 5 Q