3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a1 = ['a', 'b']; $a1 += ['b', 'c']; var_dump($a1);
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 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 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
array(2) { [0]=> string(1) "a" [1]=> string(1) "b" }

preferences:
226.7 ms | 403 KiB | 283 Q