/**
 * @param string $hex #FF0000 oder FF0000
 * @param array $default
 * @return array
 */
public static function hex2rgb(string $hex, array $default = ['r' => 0, 'g' => 0, 'b' => 0]) : array {

  if (substr($hex, 0, 1) !== '#') $hex = '#'.$hex;
  if (!preg_match('/#([a-f]|[A-F]|[0-9]){3}(([a-f]|[A-F]|[0-9]){3})?\b/', $hex)) return $default;

  $r = substr($hex, 1, 2); $r = hexdec($r);			
  $g = substr($hex, 3, 2); $g = hexdec($g);
  $b = substr($hex, 5, 2); $b = hexdec($b);

  return [
    'r' => $r,
    'g' => $g,
    'b' => $b
  ];

}