3v4l.org

run code in 300+ 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 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.25, 8.4.1 - 8.4.12
array(2) { [0]=> string(10) "string key" [1]=> int(1234567890) }
preferences:
138.18 ms | 407 KiB | 5 Q