JSON parser returns Null
JSON string : correct username and password [{"user_id":"7","first_name":"dada","last_name":"Kara","e_mail":"yaka@gmail","fullname":"Dada Kara","forum_username":"ycan"}]

-(IBAction)loginButton:(id)sender{

    NSString *username = usernameTextfield.text;
    NSString *password = passwordTextfield.text;

    NSMutableURLRequest *request =[NSMutableURLRequest requestWithURL:[NSURL URLWithString:kPostUrl]];
    [request setHTTPMethod:@"POST"];

    NSString *post =[[NSString alloc] initWithFormat:@"e_mail=%@&password=%@", username, password];
    [request setHTTPBody:[post dataUsingEncoding:NSASCIIStringEncoding]];

    NSURLResponse *response;
    NSError *err;

    NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&err];
    //NSString *responseStr = [NSString stringWithUTF8String:[responseData bytes]];
    //NSLog(@"Response : %@", responseStr);

    NSString *json_string = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
    NSLog(@"JSON string : %@", json_string);

    SBJsonParser *parser = [[SBJsonParser alloc] init];
    NSDictionary *responseObj = [parser objectWithString:json_string error:nil];
    NSArray *name = [responseObj objectForKey:@"first_name"];

    NSLog(@"Name : %@", name);
}

//trim in coming echo
    NSString *newString1 = [json_string stringByReplacingOccurrencesOfString:@"correct username and passwordn" withString:@""];



    SBJsonParser *parser = [[SBJsonParser alloc] init];

    NSArray *responseObj = [parser objectWithString:newString1 error:nil];

    NSDictionary *dataDict = [responseObj objectAtIndex:0];

    NSString *userID = [dataDict objectForKey:@"user_id"];

    NSLog(@"user_id: %@", userID);

SBJsonParser *parser = [[SBJsonParser alloc] init];

 NSArray *responseObj = [parser objectWithString:json_string error:nil];

NSDictionary *dataDict = [responseObj objectAtIndex:0];

NSString *name = [dataDict objectForKey:@"first_name"];