3v4l.org

run code in 300+ PHP versions simultaneously
<?php $array = [ [1 => 'french', 2 => 'dutch'], [1 => 'french', 3 => 'english'], [1 => 'dutch'], [4 => 'swedish'], ]; var_dump(array_unique(array_merge(...$array)));
Output for 5.6.0 - 5.6.25, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
array(4) { [0]=> string(6) "french" [1]=> string(5) "dutch" [3]=> string(7) "english" [5]=> string(7) "swedish" }
preferences:
110.28 ms | 1511 KiB | 4 Q