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<?php $a = array('person' => array( 'name' => 'franz', 'last_name' => 'de leon', )); $b = array('person' => array( 'name' => 'cheryl', )); var_dump(array_merge_recursive($a, $b));
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(1) { ["person"]=> array(2) { ["name"]=> array(2) { [0]=> string(5) "franz" [1]=> string(6) "cheryl" } ["last_name"]=> string(7) "de leon" } }

preferences:
347.16 ms | 406 KiB | 452 Q