3v4l.org

run code in 300+ PHP versions simultaneously
<?php $x = array("a", "b", "c", "d", "e"); $x = array_reduce($x, function($arr, $val) { array_push($arr, $val, $val); return $arr; }, []); var_dump($x);
Output for 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 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.25, 8.4.1 - 8.4.12
array(10) { [0]=> string(1) "a" [1]=> string(1) "a" [2]=> string(1) "b" [3]=> string(1) "b" [4]=> string(1) "c" [5]=> string(1) "c" [6]=> string(1) "d" [7]=> string(1) "d" [8]=> string(1) "e" [9]=> string(1) "e" }
preferences:
147.89 ms | 408 KiB | 5 Q