Check the latest version

<!--?php
/*
* To use, place this on a web server of your choice.  Next, create a mysql database
* where you will store information about your applications, such as the latest version.
* From now on, when you update an application, you will also need to update the
* information in the database about that application. Configure the database with the
* following columns: app_name, latest_version, build_date, url
*
* Then, in your application, when it checks for updates, have it send a request to the
* web server formed like this:
* http://myserver.com/app_updates.php?app_name=MyAppName
* where MyAppName above is exactly the same as the app_name stored in the mysql
* database. If MyAppName is found in the database, then it will return a small
* xml string with the data for that record.  If MyAppName is not found, it will
* return nothing. The xml output will look like this
*
* <?xml version="1.0"?-->
*
*   SevereWeatherGrowler
*   1.2.0
*   20110629
*   http://skipstechtalk.net/severe-weather-growler/
*
*
*
* It is up to your application to decide what to do with the returned data. For
* instance, one way to check if an update is available is to always store the build
* date in your application. Then when your application checks the sever, it can
* compare its build data to the build date for the latest version. If they are
* different, then an update is required. You can then direct the user to the url
* provided to get the update.
*/
$dbuser = 'my_database_user_name';
$dbname = 'my_database_name';
$dbpasswd = 'my_super_secret_password';
$dbhost = 'my_db_host'; // might be 'localhost'
$table_name = 'app_updates';
 
// test the connection
$dbh = @mysql_connect($dbhost, $dbuser, $dbpasswd);
if (!$dbh)
{
  echo "Could not connect to MySQL server on " . $dbhost;
  die();
}
 
// get the app_name from the url
$app_name = $_REQUEST['app_name'];
 
// get the data from the database for that app_name
$query = "SELECT * FROM $dbname.$table_name WHERE app_name = '$app_name'";
$result = query($query);
$row = mysql_fetch_object($result);
//print_r ($row);
 
// build the xml output
if ($row != null)
{
  $xmlstr = "<!--?xml version='1.0' ?-->\n";
  $xml = new SimpleXMLElement($xmlstr);
  $xml->addChild('app_name', $row->app_name);
  $xml->addChild('latest_version', $row->latest_version);
  $xml->addChild('build_date', $row->build_date);
  $xml->addChild('url', $row->url);
  //print_r($xml);
  echo $xml->asXml();
}
 
function query($query) {
  if(!($result = mysql_query($query)))
  {
    //can't execute query
    echo ( "Couldn't query table!\n");
    echo ( "MySQL Reports: " . mysql_error() . "\n" . "Query was: " . $query);
    exit();
  }
  return $result;
}
 
?&gt;

public const string UPDATE_CHECKER_URL = "http://my_webserver.com/app_updates.php";
public const int BUILD_DATE = 20110629;
 
public static void appUpdateTimer_Elapsed(object sender, ElapsedEventArgs e)
{
  try
  {
    WebClient wc = new WebClient();
    string updateCheckerUrl = UPDATE_CHECKER_URL + "?app_name=" +
         System.Windows.Forms.Application.ProductName;
    string updateText = wc.DownloadString(updateCheckerUrl);
    XmlDocument myXmlDoc = new XmlDocument();
    myXmlDoc.LoadXml(updateText);
 
    string latestVersion =
       myXmlDoc.SelectSingleNode("/appdata/latest_version").InnerText;
    string build_date =
       myXmlDoc.SelectSingleNode("/appdata/build_date").InnerText;
    string updateUrl =
       myXmlDoc.SelectSingleNode("/appdata/url").InnerText;
    int result = 0;
    Int32.TryParse(build_date, out result);
 
    if (BUILD_DATE != result)
    {
      MessageBox.Show("There is an update available. Please check " +
           updateUrl + " for details.");
    }
  }
  catch
  {
    //do nothing.
  }
}

appUpdateTimer.Interval = 4 * 60 * 60 * 1000; //check every four hours
appUpdateTimer.AutoReset = true;
appUpdateTimer.Elapsed += new ElapsedEventHandler(appUpdateTimer_Elapsed);
appUpdateTimer.Start();