3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a = [1,2,3,4,5,6,7,8,9]; foreach ($a as $key => &$value) { if ($key === 4) { unset($a[$key + 1]); var_dump(key($a)); break; } } var_dump(key($a));
Output for 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.16 - 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
int(0) int(0)
Output for 5.4.2 - 5.4.45, 5.5.24 - 5.5.35, 5.6.7 - 5.6.28
int(6) int(6)

preferences:
188.77 ms | 402 KiB | 227 Q