Online PHP editor | refs for RLS36

<?php function permuteUnique($items, $perms = [], &$return = []) { if (empty($items)) { $return[] = $perms; } else { sort($items); $prev = false; for ($i = count($items) - 1; $i >= 0; --$i) { $newitems = $items; $tmp = array_splice($newitems, $i, 1)[0]; if ($tmp != $prev) { $prev = $tmp; $newperms = $perms; array_unshift($newperms, $tmp); permuteUnique($newitems, $newperms, $return); } } return $return; } } $permutations = permuteUnique(["x1", "x2", "x3"]); var_dump($permutations);