3v4l.org

run code in 300+ PHP versions simultaneously
<?php $array = array('a' => 'Hello', 'b' => 'World'); array_walk($array, 'adda'); function adda(&$value, &$key) { $key = "a".$key; } var_dump($array);
Output for 8.0.0 - 8.0.3
Warning: adda(): Argument #2 ($key) must be passed by reference, value given in /in/b8gAJ on line 4 Warning: adda(): Argument #2 ($key) must be passed by reference, value given in /in/b8gAJ on line 4 array(2) { ["a"]=> string(5) "Hello" ["b"]=> string(5) "World" }
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 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.27, 7.4.0 - 7.4.15
array(2) { ["a"]=> string(5) "Hello" ["b"]=> string(5) "World" }