您需要将content-type标头值设置为使用JSON。
request.addValue("application/json", forHTTPHeaderField: "Content-Type")将代码更新为Swift 3，并删除了与请求无关的所有内容：
let myUrl = URL(string: "http://foodhelper.club/registerUser.php");var request = URLRequest(url:myUrl!);request.httpMethod = "POST";request.addValue("application/json", forHTTPHeaderField: "Content-Type")let postString = "userEmail=email&userFirstName=firstname&userLastName=lastname&userPassword=password";request.httpBody = postString.data(using: String.Encoding.utf8);URLSession.shared.dataTask(with: request, completionHandler: { (data:Data?, response:URLResponse?, error:Error?) -> Void in if error != nil { print("fail") return } do { let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary print ("1") if let parseJSON = json { let userId = parseJSON["userId"] as? String print ("2") if( userId != nil) { } else { let errorMessage = parseJSON["message"] as? String print ("3") } } } catch{ print(error) }}).resume()
