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<?php $a = array('a' => 1, 'ab' => 2, 'na' => null, 'nb' => 3); $b = array('b' => 10, 'ab' => 20, 'na' => 30, 'nb' => null); var_dump(array_merge($a, $b));
Output for 4.3.0 - 7.2.0
array(5) { ["a"]=> int(1) ["ab"]=> int(20) ["na"]=> int(30) ["nb"]=> NULL ["b"]=> int(10) }