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<?php final class B {} class_alias(B::class, 'a'); $serializedInstanceOfA = 'O:1:"a":0:{}'; var_dump(unserialize($serializedInstanceOfA));
Output for 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
object(B)#1 (0) { }

preferences:
58.68 ms | 978 KiB | 4 Q