3v4l.org

run code in 300+ PHP versions simultaneously
<?php $result = json_encode(['end' => json_decode(null, true)]); var_dump($result); class A implements \JsonSerializable { function jsonSerialize() { return ['end' => json_decode(null, true)]; } } $a = new A(); $toJsonData = $a->jsonSerialize(); $result = json_encode($a); var_dump($result); $result = json_encode($toJsonData); var_dump($result);
based on lIePG
Output for 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.7 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.28, 7.4.0 - 7.4.16, 8.0.0 - 8.0.3
string(12) "{"end":null}" string(12) "{"end":null}" string(12) "{"end":null}"
Output for 7.0.0 - 7.0.6
string(12) "{"end":null}" bool(false) string(12) "{"end":null}"