3v4l.org

run code in 300+ PHP versions simultaneously
<?php var_dump(key(array()));
Output for 4.4.1, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.30, 7.0.0 - 7.0.20, 7.1.0 - 7.1.9, 7.2.29 - 7.2.33, 7.3.12 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
NULL
Output for 4.3.2 - 4.3.11, 4.4.0, 4.4.2 - 4.4.9, 5.0.0 - 5.0.5
Fatal error: Only variables can be passed by reference in /in/1ugoX on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1
Fatal error: Only variables can be passed by reference in /in/1ugoX on line 3

preferences:
258.83 ms | 401 KiB | 369 Q