3v4l.org

run code in 500+ PHP versions simultaneously
<?php $array = array( 'string key' => 'aaa', '1234567890' => 'bbb' ); var_dump(array_keys($array));
Output for 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
array(2) { [0]=> string(10) "string key" [1]=> int(1234567890) }
preferences:
44.37 ms | 1365 KiB | 4 Q