code: protected static function read_2_bytes($handle)
      {
          $c1 = fgetc($handle);
          if ($c1 === false) {
              throw new \RuntimeException('Premature EOF in JPEG file', 1363533326);
          }
          $c2 = fgetc($handle);
          if ($c2 === false) {
              throw new \RuntimeException('Premature EOF in JPEG file', 1363533326);
          }
          return (ord($c1) << 8) + (ord($c2));
      }
docs: Reads 2 bytes, converts them to unsigned int
  Remark: All 2-byte quantities in JPEG markers are MSB first.
  
  @param resource $handle
  @return integer
  @throws \RuntimeException