ios - AFHTTPRequestOperationManager 给出请求失败错误

Question

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

manager.requestSerializer = [AFHTTPRequestSerializer serializer]; //not working with or without this.

NSDictionary *parameters = [NSDictionary dictionaryWithObjectsAndKeys:@"id", @"id", @"pwd", @"pwd", @"func", @"func", nil];

[manager POST:@"http://someurl.com/abc/func.php" parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {
    NSLog(@"Success: %@", responseObject);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error: %@", error);
}];

为什么我得到

错误域=AFNetworkingErrorDomain 代码=-1016“请求失败：不可接受的内容类型：文本/html” UserInfo=0x1f89e740 {NSErrorFailingURLKey= http://someurl.com/abc/func.php，AFNetworkingOperationFailingURLResponseErrorKey=，NSLocalizedDescription=请求失败：不可接受内容类型：文本/html}