3v4l.org

run code in 300+ PHP versions simultaneously
<?php $array = [ ':username:' => 'John Doe' ]; foreach($array as $sel) { // $sel's name === ':username:'. // how can I get the name, and not the value? }
Output for 7.0.0 - 7.0.20, 7.1.0 - 7.1.25, 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 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.7

preferences:
145.05 ms | 404 KiB | 183 Q