Objective c post request not sending the data

Good day.Im trying to send simple post data to server.This is the code how i do it.

 -(void)makeRequest:(NSString*)stringParameters{
    NSError *error;

    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
    NSURL *url = [NSURL URLWithString:@"http://vaenterprises.webatu.com/Authentication.php"];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
                                                           cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                       timeoutInterval:60.0];

    [request addValue:@"application/text" forHTTPHeaderField:@"Content-Type"];
    [request addValue:@"application/text" forHTTPHeaderField:@"Accept"];
    [request setHTTPMethod:@"POST"];
     NSString* postData = @"tag=hello&username=yo&something=something";
    [request setHTTPBody:postData];



    NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {

        [self parseJson:data];
    }];

    [postDataTask resume];


}

It looks great till i echo the whole post from php side like this

echo json_encode($_POST);

and i print the result in the iOS like this

-(void)parseJson:(NSData*) data{
    NSString *myString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSError *jsonError = nil;
    NSDictionary* jsonObject= [NSJSONSerialization JSONObjectWithData:data options:0 error:&jsonError];
    NSLog(@"%@",myString);
}

this issue is that i get empty string..so it means that post data not being send and that is 10000 percent objective c side issue and i have no clue why its so as in this method we only got setHttpBody with the actual string which contains key and value separated by & but that data not being send as you can see.So what am i doing wrong?Please tell somebody

Copyright Notice：Content Author:「Ios Dev」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/35112982/objective-c-post-request-not-sending-the-data