--TEST-- json_encode() Recursion test with JsonSerializable and serialize --FILE-- $this->a ]; } public function jsonSerialize(): mixed { return [ 'serialize' => serialize($this) ]; } } class SerializeFirstTest implements JsonSerializable { public $a = 1; public function __serialize() { return [ 'result' => json_encode($this) ]; } public function jsonSerialize(): mixed { return [ 'json' => serialize($this) ]; } } var_dump(json_encode(new JsonEncodeFirstTest())); var_dump(serialize(new SerializeFirstTest())); ?> --EXPECT-- string(68) "{"serialize":"O:19:\"JsonEncodeFirstTest\":1:{s:6:\"result\";i:1;}"}" string(113) "O:18:"SerializeFirstTest":1:{s:6:"result";s:62:"{"json":"O:18:\"SerializeFirstTest\":1:{s:6:\"result\";b:0;}"}";}"