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<?php class A implements Serializable { function __construct($o) { $this->o =& $o; } function serialize() { return serialize([&$this->o]); } function unserialize($s) { $this->o =& unserialize($s)[0]; } } $o = [new stdClass]; $r = unserialize(serialize([new A($o), new A($o)])); var_dump($r[0]->o[0] === $r[1]->o[0]);

preferences:
87.37 ms | 2720 KiB | 5 Q