Parse error: syntax error, unexpected 'mysqli_stmt_bind_param' (T_STRING) in C:xampphtdocsattendanceradio.php on line 19

<?php

    $user = 'root';
    $pass = '';
    $db = 'testuser';

    $con=mysqli_connect('localhost', $user, $pass, $db) or die('Unable to connect');
    mysql_select_db($testuser) or die(mysql_error());

    $userid = $_POST['userid'];
    $eventid = $_POST['eventid'];
    $attending = $POST['attending'];

    $statement = mysqli_prepare($con,
    'INSERT INTO user_has_event(user_user_id, event_event_id, attendance)
        VALUES ($userid, $eventid, $attending)
        ON DUPLICATE KEY UPDATE attendance = $attending')

    mysqli_stmt_bind_param($statement, 'iii', $userid, $eventid, $attending);
    mysqli_stmt_execute($statement);

    mysqli_stmt_store_result($statement);
    mysqli_stmt_bind_result($statement, $userid, $eventid, $eventradio);

    mysqli_stmt_close($statement);

    mysqli_close($con);
?>

public class ServerRequests {

    ProgressDialog progressDialog;
    public static final int CONNECTION_TIMEOUT = 1000 * 15;
    public static final String SERVER_ADDRESS = "http://10.0.2.2:80/";//Connects to the emulator

    public ServerRequests(Context context) {
        progressDialog = new ProgressDialog(context);
        progressDialog.setCancelable(false);
        progressDialog.setTitle("Processing");
        progressDialog.setMessage("Please wait...");
    }

    public void GetAttendanceDataAsyncTask(Attendance attendance, GetAttendanceCallback attendanceCallBack) {
        progressDialog.show();
        new getAttendanceDataAsyncTask(attendance, attendanceCallBack).execute();
    }
public class getAttendanceDataAsyncTask extends AsyncTask<Void, Void, Void> {
        Attendance attendance;
        GetAttendanceCallback attendanceCallBack;

        public getAttendanceDataAsyncTask(Attendance attendance, GetAttendanceCallback attendanceCallBack) {
            this.attendance = attendance;
            this.attendanceCallBack = attendanceCallBack;
        }

        @Override
        protected Void doInBackground(Void... params) {
            Map<String, String> dataToSend = new HashMap<>();
            dataToSend.put("userid", MainActivity.getUserID() + "");
            dataToSend.put("eventid", EventPage.getEventID() + "");
            dataToSend.put("attending", EventPage.getRadio() + "");

            String encodedStr = StrEncoder.getEncodedData(dataToSend);

            BufferedReader reader = null;

            try {
                URL url = new URL(SERVER_ADDRESS + "/attendanceradio.php");

                HttpURLConnection con = (HttpURLConnection) url.openConnection(); //Opens attendanceradio.php

                con.setConnectTimeout(CONNECTION_TIMEOUT); //Setting timeouts
                con.setReadTimeout(CONNECTION_TIMEOUT);

                con.setRequestMethod("POST"); //Request post

                con.setDoOutput(true);
                OutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream());

                writer.write(encodedStr);
                writer.flush();


                StringBuilder sb = new StringBuilder();
                reader = new BufferedReader(new InputStreamReader(con.getInputStream()));

                String line;
                while ((line = reader.readLine()) != null) { //Read until there is something available
                    sb.append(line + "n");     //Read and save line by line
                }
                line = sb.toString();           //Saving complete data received in string

                //Check values received in Logcat
                Log.i("custom_check", "The values received in the store part are as follows:");
                Log.i("custom_check", line);

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (reader != null) {
                    try {
                        reader.close();     //Closing the
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
            return null;
        }}