Online PHP editor | refs for dcSNo

<?php $muLevelIds = []; $subjectLevelIds = [1,6,7,8]; $occLevelIds = [6,7]; var_dump(array_union($muLevelIds, $subjectLevelIds, $occLevelIds)); function array_union($muLevelIds, $subjectLevelIds, $occLevelIds) { $allLevelIds = [1,6,7,8,9]; if (!empty($muLevelIds) && !empty($subjectLevelIds) && !empty($occLevelIds)) { $combined = array_intersect($allLevelIds, $muLevelIds, $subjectLevelIds, $occLevelIds); } elseif (empty($muLevelIds) && !empty($subjectLevelIds) && !empty($occLevelIds)) { $combined = array_intersect($allLevelIds, $subjectLevelIds, $occLevelIds); } elseif (!empty($muLevelIds) && empty($subjectLevelIds) && !empty($occLevelIds)) { $combined = array_intersect($allLevelIds, $muLevelIds, $occLevelIds); } elseif (!empty($muLevelIds) && !empty($subjectLevelIds) && empty($occLevelIds)) { $combined = array_intersect($allLevelIds, $muLevelIds, $subjectLevelIds); } return $combined; }