3v4l.org

run code in 300+ PHP versions simultaneously
<?php $array = ['a' => 1, 'b' => 2]; foreach($array as $a) { var_dump(key($array)); }
Output for 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 - 8.1.29, 8.2.0 - 8.2.21, 8.3.0 - 8.3.9
string(1) "a" string(1) "a"
Output for 5.6.38
string(1) "b" string(1) "b"

preferences:
174.11 ms | 402 KiB | 186 Q