3v4l.org

run code in 300+ PHP versions simultaneously
<?php $array = array('a' => 1, 'b' => 2, 'c' => 3); var_dump(key($array)); foreach($array as $a) { var_dump(key($array)); }
Output for 4.3.0 - 4.3.11, 4.4.0, 4.4.2 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.3, 7.0.0 - 7.0.32, 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 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
string(1) "a" string(1) "a" string(1) "a" string(1) "a"
Output for 5.2.4 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.38
string(1) "a" string(1) "b" string(1) "b" string(1) "b"
Output for 4.4.1
string(1) "a" string(1) "b" string(1) "c" NULL

preferences:
303.13 ms | 401 KiB | 414 Q