3v4l.org

run code in 300+ PHP versions simultaneously
<?php $res = array( array('a'=>'aa','b'=>'bb'), array('a'=>'aaa','b'=>'bbb') ); $res = $res + array( array('a'=>'a','b'=>'b') ); var_dump($res); $res += array( array('a'=>'aa','b'=>'bb') );
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 - 5.6.40, 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 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
array(2) { [0]=> array(2) { ["a"]=> string(2) "aa" ["b"]=> string(2) "bb" } [1]=> array(2) { ["a"]=> string(3) "aaa" ["b"]=> string(3) "bbb" } }

preferences:
288.26 ms | 406 KiB | 457 Q