3v4l.org

run code in 300+ PHP versions simultaneously
<?php $array = array( 0 => array('user_id' => '1', 'email'=>'email1'), 1 => array('user_id' => '2', 'email'=>'email2'), 2 => array('user_id' => '3', 'email'=>'email3') ); var_dump(array_keys($array));
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.8 - 5.6.21, 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 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 - 8.1.27, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
array(3) { [0]=> int(0) [1]=> int(1) [2]=> int(2) }
preferences:
236.14 ms | 405 KiB | 355 Q