Question

My iPhone app communicates through a php file with my mySql database. Everything works fine. But when I send the form and the username already exists, the php file should somehow backfire a notification. What should I do ?

php File

$query = "SELECT username FROM userData WHERE username = '$username'";  
    $result = mysql_query($query);  
    if (mysql_num_rows($result) > 0) { 
    // WHAT SHOULD BE DONE HERE TO NOTIFY iPHONE ? 
    }

I could think of a way, but it I think there is a better and more efficient way to do it.

[EDIT]

This is what I did to get the response:

 NSURLResponse *theResponse =[[NSURLResponse alloc]init];
        NSError *error;
        NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&theResponse error:&error];      

         NSDictionary *jsonDictionaryResponse =[NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
        NSLog(@"json response = %@", jsonDictionaryResponse);

[/EDIT]

Answer 1

He does not really need a push notification. Just need a response back from the server.

$query = "SELECT username FROM userData WHERE username = '$username'";  
$result = mysql_query($query);  
if (mysql_num_rows($result) > 0) { 
// WHAT SHOULD BE DONE HERE TO NOTIFY iPHONE ? 
sendResponse(200, json_encode('SUCCESS Notification'));
}

Where sendResponse looks like this

// Helper method to send a HTTP response code/message

function sendResponse($status = 200, $body = '', $content_type = 'text/html')
{
    $status_header = 'HTTP/1.1 ' . $status . ' ' . 'OK';
    header($status_header);
    header('Content-type: ' . $content_type);
    echo $body;
}