Print all possible combinations of strings that can be made using a keypad given a number

telKeys("2133004655", "2133004655", 0, 10);

$keypad = array("ABC", "DEF", "GHI", "JKL", "MNO", "PQR", "STU", "VWX", "YZ");
function telKeys($original, $new, $start, $strLength) {
  global $keypad;
  if ($start === $strLength) {
    var_dump($new);
    return;
  }

    $new[$start] = $keypad[$original[$start]][0];
    telKeys($original, $new, $start+1, $strLength);
    
    $new[$start] = $keypad[($original[$start])][1];
    telKeys($original, $new, $start+1, $strLength);
    
    if(($original[$start]) < 8) {
        $new[$start] = $keypad[($original[$start])][2];
        telKeys($original, $new, $start+1, $strLength);
    }
}