Json Request in iphone
NSString *postStr = [NSString stringWithFormat:@"username=%@&password=%@", username, password];
NSData *postData = [postStr  dataUsingEncoding:NSUTF8StringEncoding];
NSMutableURLRequest *requesting = [[NSMutableURLRequest alloc] initWithURL:YourURLObject];
[requesting setHTTPMethod:@"POST"];
[requesting setValue:[NSString stringWithFormat:@"%d", [postData length]] forHTTPHeaderField:@"Content-Length"];
[requesting setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[requesting setHTTPBody:postData];
NSError *error;
NSHTTPURLResponse *response;
[NSURLConnection sendSynchronousRequest:requesting returningResponse:&response error:&error];

NSArray *credentials = [NSArray arrayWithObjects:@"uName", @"pWord",nil];
NSString *jsonString = [credentials JSONString];

NSDictionary *credentials = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"uName", @"pWord",nil] forKeys:[NSArray arrayWithObjects:@"UserName",@"password",nil]];
NSString *jsonString = [credentials JSONString];