当数据通过ios时，json_decode返回null

this problem is very tricky. when I pass json data through IOS by using AFNetworking. the server also return null value. However, I used curl to test server side, the result is correct. I have no idea about this problem.

Here is server code:

        $response['return'] = $data;

        if (get_magic_quotes_gpc()) {
            $data = stripslashes($data);
        }

        $response['sssss'] = $data;

        $data = json_decode($data, TRUE);
        $response['return json'] = $data ? $data : 'dddddddd';

        $json_errors = array(
            JSON_ERROR_NONE => 'No error has occurred',
            JSON_ERROR_DEPTH => 'The maximum stack depth has been exceeded',
            JSON_ERROR_CTRL_CHAR => 'Control character error, possibly incorrectly encoded',
            JSON_ERROR_SYNTAX => 'Syntax error',
        );
        $response['json error'] = $json_errors[json_last_error()];

        $response['p'] = $data->name;

        $response['d'] = 'test';

ios code :

        NSURL *url = [NSURL URLWithString:@"myapi"];
        AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:url];
        [httpClient setDefaultHeader:@"Accept" value:@"application/json"];
        [httpClient registerHTTPOperationClass:[AFJSONRequestOperation class]];
        [httpClient setParameterEncoding:AFJSONParameterEncoding];

        NSDictionary *parameters = [NSDictionary dictionaryWithObjectsAndKeys:dishParameter,@"dish", nil];
        [httpClient postPath:@"dish" parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {

            for (id key in responseObject) {
                NSLog(@"key:%@   value:%@", key, [responseObject objectForKey:key]);
            }


        } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
             NSLog(@"error:%@",error);
        }];

the response said that no syntax error and server can get the value of dish parameter. but when $data through stripslashes function, $data becomes to null.

Anyone can give me some suggestion?

$data is type string? Why would you strip slashes from JSON? You screw the syntax. Do not do that. json_decode returns null becauuse it's an invalid JSON format.