在 iOS 应用程序中返回 JSON

我正在尝试通过PHP文件在我的iOS应用程序中返回一个简单的JSON。

.PHP：

<?php
header('Content-Type: application/json');
$myarray = array("io" => 1, "tu" => 2);
$out = json_encode($myarray);
echo $out;
?>

苹果：

-(void)provePHP{
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
    [request setURL:[NSURL URLWithString:@"http://mysite/myphpfile.php"]];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [request setValue:@"application/json"forHTTPHeaderField:@"Content-Type"];
    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    [connection start];
}
- (void)connection:(NSURLConnection *)connection
    didReceiveData:(NSData *)data{
    NSError *error;
    NSDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableContainers error: &error];
    NSLog(@"%@ - %@", jsonDict, error);
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    NSLog(@"FINISH");
}
- (void)connection:(NSURLConnection *)connection
  didFailWithError:(NSError *)error{
    NSLog(@"Error");
}

我不明白我做错了什么。我遵循了在这个网站上找到的许多代码，但日志中没有结果。