code: private function writeUrl($row, $col, $url)
      {
          // Add start row and col to arg list
          return $this->writeUrlRange($row, $col, $row, $col, $url);
      }
docs: Write a hyperlink.
  This is comprised of two elements: the visible label and
  the invisible link. The visible label is the same as the link unless an
  alternative string is specified. The label is written using the
  writeString() method. Therefore the 255 characters string limit applies.
  $string and $format are optional.
  
  The hyperlink can be to a http, ftp, mail, internal sheet (not yet), or external
  directory url.
  
  Returns  0 : normal termination
  -2 : row or column out of range
  -3 : long string truncated to 255 chars
  
  @param int $row Row
  @param int $col Column
  @param string $url URL string
  
  @return int