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<?php $root = array( 1=>'cat1', 2=>'cat2', 3=>'cat3' ); $child_1 = array( 1=>'sub_cat1', 2=>'sub_cat2', 3=>'sub_cat3' ); $child_2 = array( 1=>'sub_sub_cat1', 2=>'sub_sub_cat2', 3=>'sub_sub_cat3' ); function getAllCombinationsArray($source_arrays = array(), $kd = array(), $vd = array()){ $return = array(); foreach(array_shift($source_arrays) as $ck => $cv) { if(!empty($source_arrays)) { $return += getAllCombinationsArray($source_arrays, $kd + $ck, $vd + $cv); } else { $return[implode('_', $kd)] = implode(' -> ', $vd); } } return $return; } print_r(getAllCombinationsArray(array($root, $child_1, $child_2)));

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