iOS - ทำหน้า login php mysql แต่มันไม่ส่งค่า json มาให้ค่ะ

//
//  ViewController.m
//  LoginScreenTutorial
//
//  Created by Dipin Krishna on 26/12/13.
//  Copyright (c) 2013 Dipin Krishna. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)sigininClicked:(id)sender {
    NSInteger success = 0;
    @try {
        
        if([[self.Username text] isEqualToString:@""] || [[self.Password text] isEqualToString:@""] ) {
            
            [self alertStatus:@"Please enter Email and Password" :@"Sign in Failed!" :0];
            
        } else {
            NSString *post =[[NSString alloc] initWithFormat:@"Idname=%@&password=%@",[self.Username text],[self.Password text]];
            NSLog(@"PostData: %@",post);
            
            NSURL *url=[NSURL URLWithString:@"http://localhost:8888/loginfile.php"];
            
            NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
            
            NSString *postLength = [NSString stringWithFormat:@"%lu", (unsigned long)[postData length]];
            
            NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
            [request setURL:url];
            [request setHTTPMethod:@"POST"];
            [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
            [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
            [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
            [request setHTTPBody:postData];
            
            //[NSURLRequest setAllowsAnyHTTPSCertificate:YES forHost:[url host]];
            
            NSError *error = [[NSError alloc] init];
            NSHTTPURLResponse *response = nil;
            NSData *urlData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
            
            NSLog(@"Response code: %ld", (long)[response statusCode]);
            
            if ([response statusCode] >= 200 && [response statusCode] < 300)
            {
                NSString *responseData = [[NSString alloc]initWithData:urlData encoding:NSUTF8StringEncoding];
                NSLog(@"Response ==> %@", responseData);
                
                NSError *error = nil;
                NSDictionary *jsonData = [NSJSONSerialization
                                          JSONObjectWithData:urlData
                                          options:NSJSONReadingMutableContainers
                                          error:&error];
                
                success = [jsonData[@"success"] integerValue];
                NSLog(@"Success: %ld",(long)success);
                
                if(success == 1)
                {
                    NSLog(@"Login SUCCESS");
                } else {
                    
                    NSString *error_msg = (NSString *) jsonData[@"error_message"];
                    [self alertStatus:error_msg :@"Sign in Failed!" :0];
                }
                
            } else {
                //if (error) NSLog(@"Error: %@", error);
                [self alertStatus:@"Connection Failed" :@"Sign in Failed!" :0];
            }
        }
    }
    @catch (NSException * e) {
        NSLog(@"Exception: %@", e);
        [self alertStatus:@"Sign in Failed." :@"Error!" :0];
    }
    if (success) {
        [self performSegueWithIdentifier:@"login_success" sender:self];
    }
}

- (void) alertStatus:(NSString *)msg :(NSString *)title :(int) tag
{
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:title
                                                        message:msg
                                                       delegate:self
                                              cancelButtonTitle:@"Ok"
                                              otherButtonTitles:nil, nil];
    alertView.tag = tag;
    [alertView show];
}

- (IBAction)backgroundTap:(id)sender {
    [self.view endEditing:YES];
}

-(BOOL) textFieldShouldReturn:(UITextField *)textField {
    [textField resignFirstResponder];
    return YES;
}

@end

<?php

$host = "localhost"; 
$user = "root"; 
$pass = "root"; 
$db="student2";

$r = mysql_connect($host, $user, $pass);

if (!$r) {
    echo "Could not connect to server\n";
    trigger_error(mysql_error(), E_USER_ERROR);
} else {
    echo "Connection established\n"; 
}

echo mysql_get_server_info() . "\n"; 
$r2 = mysql_select_db($db);

if (!$r2) {
    echo "Cannot select database\n";
     trigger_error(mysql_error(), E_USER_ERROR);
} else {
    echo "database selected\n"; 
}
$u=$_POST['Username'];
$pw=$_POST['Password'];
$result=mysql_query("select sIdname,password from student where Idname='$u' and      password='$pw'");

$row=mysql_fetch_array($result);
if($row["Idname"]==$u && $row["password"]==$pw)
{
echo '{"success":1}';

	
}
else
{
 '{"success":0,"error_message":"Username and/or password is invalid."}';
 
echo json_encode(array("key" => $result));  
 }
   mysql_close();

  ?>