Online PHP editor | refs for Lfq4C

<?php // array of characters depending on other characters $characters = array( 'a' => array('c'), 'b' => array('c', 'a'), 'd' => array('c', 'a'), 'c' => array(), 'l' => array('c'), 'f' => array('l'), 't' => array('a'), 'w' => array('c', 'a'), ); function sortCharacters($characters) { uksort ($characters, function ($a, $b) use ($characters) { if (empty($characters[$a]) && empty($characters[$b])) { // equal (no dependencies) return 0; } if (empty($characters[$a]) && !empty($characters[$b])) { // a has no dependencies so is lower return -1; } if (!empty($characters[$a]) && empty($characters[$b])) { // b has no dependencies so a is higher return 1; } if (in_array($a, $characters[$b])) { // b depends on a so a is lower return -1; } if (in_array($b, $characters[$a])) { // a depends on b so a is higher return 1; } return 0; }); return $characters; } $characters = sortCharacters($characters); print_r($characters);