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<?php class A {} class B extends A{} $b = 'B'; var_dump(is_subclass_of('A', 'A'), is_subclass_of('B', 'A'), is_subclass_of($b, 'A')); var_dump(is_a('A', 'A'), is_a('B', 'A'), is_a($b, 'A'));

preferences:
37.47 ms | 402 KiB | 5 Q