How do I correct this flutter error: Unexpected token a in JSON at position 0?

Question

When I send data from flutter to php I am getting the error below. I am using dropdown and map to display and collect the date selection. I also have a few text boxes Error: FormatException: SyntaxError: Unexpected token a in JSON at position 0 at Object.throw_ [as throw] (http://localhost:50857/dart_sdk.js:5334:11)

Future _submitemail() async {
  var apiUrl = "http://www.redhowler.com/db/signup.php";

 String date = year +'-'+ month +'-'+ day;
 print(date);
  Map mappedData = {
   'email': _email.text,
   'date': date
  };
  http.Response response = await http.post(apiUrl, body: mappedData);
  var data = jsonDecode(response.body);
  print(data);
}
}

Answer 1

To solve this problem I format the body data the way it is display on the form. I capture date first, then email. So I changed the mappedData. Look at the code when I first post the problem compare to the code below.

Future _submitemail() async {
  var apiUrl = "http://www.redhowler.com/db/signup.php";

 String date = year +'-'+ month +'-'+ day;
 print(date);
  Map mappedData = {
   'date': date,
   'email': _email.text
  };
  http.Response response = await http.post(apiUrl, body: mappedData);
  var data = jsonDecode(response.body);
  print(data);
}
}