3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a = array( array('a1'), array('a2'), array('a3'), array('a4'), ); $b = array( array('b1'), ); $c = $a + $b; var_dump($c);
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, 5.5.0 - 5.5.38, 5.6.0 - 5.6.38, 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 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
array(4) { [0]=> array(1) { [0]=> string(2) "a1" } [1]=> array(1) { [0]=> string(2) "a2" } [2]=> array(1) { [0]=> string(2) "a3" } [3]=> array(1) { [0]=> string(2) "a4" } }

preferences:
332.03 ms | 406 KiB | 454 Q