Unable to send data to server in Android

Question

I'm new to Android. Don't know which part has gone wrong. The thing is I'm unable to send the data to the server in Android Studio.

This is the error I'm facing

Fatal error: Uncaught Error: Call to undefined function mysql_connect() in C:\xampp\htdocs\students\connection.php:6 Stack trace: #0 C:\xampp\htdocs\students\add_employee.php(2): include() #1 {main} thrown in C:\xampp\htdocs\students\connection.php on line 6

The code goes like this...

Main Activity

public class MainActivity extends AppCompatActivity  {

Button b1;
EditText e1;
private ProgressDialog pDialog;
private JSONObject json;
private int success=0;
private HTTPURLConnection service;
private String strname ="";
//Initialize webservice URL
private String path = "http://localhost/student/add_employee.php";





@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    b1 = (Button) findViewById(R.id.button);
    e1 = (EditText) findViewById(R.id.editText9);

    service=new HTTPURLConnection();


    b1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (!e1.getText().toString().equals("") ) {
                strname = e1.getText().toString();

                //Call WebService
                new PostDataTOServer().execute();
            } else {
                Toast.makeText(getApplicationContext(), "Please Enter all fields", Toast.LENGTH_LONG).show();
            }


            Intent intent = new Intent(MainActivity.this, Student1.class);
            startActivity(intent);

    }
});
}

private class PostDataTOServer extends AsyncTask<Void, Void, Void> {

String response = "";
//Create hashmap Object to send parameters to web service
HashMap<String, String> postDataParams;
@Override
protected void onPreExecute() {
    super.onPreExecute();

    pDialog = new ProgressDialog(MainActivity.this);
    pDialog.setMessage("Please wait...");
    pDialog.setCancelable(false);
    pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
    postDataParams=new HashMap<String, String>();
    postDataParams.put("name", strname);

    //Call ServerData() method to call webservice and store result in response
    response= service.ServerData(path,postDataParams);
    try {
        json = new JSONObject(response);
        //Get Values from JSONobject
        System.out.println("success=" + json.get("success"));
        success = json.getInt("success");

    } catch (JSONException e) {
        e.printStackTrace();
    }
    return null;
}
@Override
protected void onPostExecute(Void result) {
    super.onPostExecute(result);
    if (pDialog.isShowing())
        pDialog.dismiss();
    if(success==1) {
        Toast.makeText(getApplicationContext(), "Employee Added successfully..!", Toast.LENGTH_LONG).show();
    }
}
}
}

HTTPURLConnection

public class HTTPURLConnection {
String response="";
URL url;
public String ServerData(String path,HashMap<String, String> params) {
    try {
        url = new URL(path);

        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(15000);
        conn.setConnectTimeout(15000);
        conn.setRequestMethod("POST");
        conn.setDoInput(true);
        conn.setDoOutput(true);


        OutputStream os = conn.getOutputStream();
        BufferedWriter writer = new BufferedWriter(
                new OutputStreamWriter(os, "UTF-8"));
        writer.write(getPostDataString(params));

        writer.flush();
        writer.close();
        os.close();
        int responseCode = conn.getResponseCode();

        if (responseCode == HttpsURLConnection.HTTP_OK) {
            String line;
            BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            //Log.d("Output",br.toString());
            while ((line = br.readLine()) != null) {
                response += line;
                Log.d("output lines", line);
            }
        } else {
            response = "";
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return response;
}

private String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException {
    StringBuilder result = new StringBuilder();
    boolean first = true;
    for(Map.Entry<String, String> entry : params.entrySet()){
        if (first)
            first = false;
        else
            result.append("&");

        result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
        result.append("=");
        result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
    }

    return result.toString();
}}

My PHP code

add_employee.php

<?php
include('connection.php');
$emp_name=$_POST["name"];
$success=0;
$status="Active";
$sql = "INSERT INTO  `employee` (`emp_name`) 
VALUES ('$emp_name')";
if(mysql_query($sql))
{
$success=1;
}
$response["success"]=$success;
die(json_encode($response));
mysql_close($con);
?>

connection.php

<?php
 $dbhost = 'localhost';
$dbuser = 'root';
$dbpass = '';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);    
if(!$conn) {
    die('Could not connect: ' . mysql_error());
}
mysql_select_db('student');
?>