Estoy creando una aplicación que requiere insertar una fila en una base de datos mysql (alojada en línea), sin embargo, cada vez que intento insertar los datos, los datos están en blanco. no hay nada malo con el php, ya que mi front-end web funciona perfectamente con el script php.

NSString *user = self.registerUsername.text;
NSString *password = self.registerPassword.text;
NSString *email = self.registerEmail.text;
NSString *model = [NSString stringWithFormat:@"%@", [[UIDevice currentDevice] model]];
NSString *sysVer = [NSString stringWithFormat:@"%@", [[UIDevice currentDevice] systemVersion]];

NSString *connectionURL = @"mydomain.com/Register.php";
NSLog(@"%@", connectionURL);
//this is logged correctly

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:[NSURL URLWithString:connectionURL]];
[request setHTTPMethod:@"POST"];

NSString *insert = [[NSString alloc] initWithFormat:@"username=%@&password=%@&email=%@&model=%@&sysver=%@", user, password, email, model, sysVer];

NSLog(@"%@", insert);
[request setHTTPBody:[insert dataUsingEncoding:NSASCIIStringEncoding]];
//This is also logged correctly, giving me the right format i would expect

NSURLResponse *response;
NSError *error;
NSData *responseData = [NSURLConnection sendSynchronousRequest:request                             returningResponse:&response error:&error];

NSString *responseString = [NSString stringWithUTF8String:[responseData bytes]];
NSLog(@"%@", responseString);
//The response string is also correct, but no data is inserted into the database

NSString *success = @"success";
[success dataUsingEncoding:NSUTF8StringEncoding];

NSLog(@"%lu", (unsigned long)responseString.length);
NSLog(@"%lu", (unsigned long)success.length);

mRegister.php

<?php

header('Content-type: text/plain; charset=utf-8');

include("config/dp.php"); //<- db connection

$con = mysql_connect("127.0.0.1","user","pass");
if(! $con)
{
die('Connection Failed'.mysql_error());
}

mysql_select_db("hk", $con);

$message = "";

$username = ($_POST['username']); 
$password = ($_POST['password']);
$email = ($_POST['email']);
$model = ($_POST['model']);
$sysver = ($_POST['sysver']);

$submit = $_POST["registerform"];

$sql = "INSERT INTO members (`username`, `password`, `email`, `model`, `sysver`) VALUES ('$username', '$password', '$email', '$model', '$sysver')";
$result = mysql_query($sql);

$row = mysql_fetch_array($result);

if ($result) { $message = "success"; }
else { $message = "failed"; }

echo utf8_encode($message);

?> 

además,responseString por lo general aparece con algunos personajes extraños después de que por lo tanto afecta a laresponseString.length valor. ¿Hay algún problema con mi código o tiene que ver con mi php?