Enables or disables the WLAN guest access of a Fritz!Box
 
 Usage on UNIX systems:
   /path/to/php ' . $argv[0] . ' {0|1} [optional: PASSWORD]
 
 Usage on Windows systems:
   c:\\path\\to\\php.exe ' . $argv[0] . ' {0|1} [optional: PASSWORD]
 
 0 disables the guest access
 1 enables the guest access
 
 The optional argument PASSWORD sets a new guest access password (min 8 chars)
 Defaults to false, so the current password is kept.
 ';
       } else {
           $fritz->logMessage($message . 'ERROR: Script was called without or with an invalid argument');
       }
       exit;
   }
   $wpa_key = isset($argv[2]) && strlen($argv[2]) >= 8 && strlen($argv[2]) <= 63 ? $argv[2] : false;
   // read the current settings
   $formfields = array('getpage' => '/wlan/guest_access.lua');
   $output = $fritz->doGetRequest($formfields);
   // read down_time_activ setting
   preg_match('@name="down_time_activ"[^>]+(checked)[^>]*@', $output, $matches);
   if (isset($matches[1])) {
       $formfields['down_time_activ'] = 'on';
   }
   // read down_time_value setting
   preg_match('@name="down_time_value".*?<option value="(\\d+)"[^>]+?selected.*?</select>@s', $output, $matches);
   $formfields['down_time_value'] = isset($matches[1]) ? $matches[1] : '15';