<?php #$nums = [2,7,11,15]; #$comp_num = 9; #$nums = [3,3]; $comp_num = 6; $nums = [3,2,4]; $nums_dict = array(); for ($i = 0; $i < count($nums); $i++) { $current_map_val = $nums_dict[$nums[$i]]; if ($current_map_val > 0) { $return_array = array($current_map_val,$i); var_dump($return_array); } else { $difference = $comp_num - $nums[$i]; $nums_dict[$difference] = $i; } } #var_dump($nums_dict);