3v4l.org

run code in 300+ PHP versions simultaneously
<?php $v = array(1,2,3,4,2,3); $keys = array_keys($v, '2'); print_r($keys);
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.27, 8.0.0 - 8.0.15, 8.1.0 - 8.1.2
Array ( [0] => 1 [1] => 4 )

preferences:
198.61 ms | 461 KiB | 5 Q