code: public static function supportedEncodings()
      {
          if (static::$supported_encodings === null) {
              $supported = mb_list_encodings();
  
              foreach ($supported as $key => $value) {
                  static::$supported_encodings[strtolower($value)] = $value;
  
                  foreach (mb_encoding_aliases($value) as $k => $v) {
                      static::$supported_encodings[strtolower($v)] = $value;
                  }
              }
          }
  
          return static::$supported_encodings;
      }
docs: Creates an array with all of the aliases->encodings
  
  @return array