3v4l.org

run code in 300+ PHP versions simultaneously
<?php $arr = [1, 2, 3, 4, 5, 6, 7]; echo key($arr).PHP_EOL; next($arr); echo key($arr).PHP_EOL;
Output for 5.5.0 - 5.5.38, 5.6.0 - 5.6.38, 7.0.0 - 7.0.33, 7.1.0 - 7.1.25, 7.2.0 - 7.2.33, 7.3.0 - 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
0 1
preferences:
252.62 ms | 404 KiB | 294 Q