字符串作为整数传递

Im making an Android application where I have a registration page that saves users to the database. But for some reason the username section keeps being sent as an integer (if I enter a String it will send '0' if enter a number it will send that correct number) but the value is declared as a String???

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);

        final EditText etName = (EditText) findViewById(R.id.etName);
        final EditText etUsername = (EditText) findViewById(R.id.etUsername); //This variable here
        final EditText etEmail = (EditText) findViewById(R.id.etEmail);
        final EditText etPassword = (EditText) findViewById(R.id.etPassword);

        final Button bRegister = (Button) findViewById(R.id.bRegister);

        bRegister.setOnClickListener(new View.OnClickListener(){
           @Override
            public void onClick(View v) {
               final String name = etName.getText().toString();
               final String username = etUsername.getText().toString();
               final String email = etEmail.getText().toString();
               final String password = etPassword.getText().toString();

               Response.Listener<String> responseListener = new Response.Listener<String>(){

                   @Override
                   public void onResponse(String response){
                       try {
                           JSONObject jsonResponse = new JSONObject(response);
                           boolean success = jsonResponse.getBoolean("success");

                           if (success){
                               Intent intent = new Intent(RegisterActivity.this, LoginActivity.class);
                               RegisterActivity.this.startActivity(intent);
                           }
                           else{
                               AlertDialog.Builder builder = new AlertDialog.Builder(RegisterActivity.this);
                               builder.setMessage("Registration Failed")
                                       .setNegativeButton("Retry", null)
                                       .create()
                                       .show();
                           }
                       }
                       catch(JSONException E){
                           E.printStackTrace();
                       }
                   }

               };
               RegisterRequest registerRequest = new RegisterRequest( name,username, email,password,responseListener);
               RequestQueue queue = Volley.newRequestQueue(RegisterActivity.this);
               queue.add(registerRequest);
           }
        });

REQUEST:

public class RegisterRequest extends StringRequest {

    private static final String REGISTER_REQUEST_URL = "server link";
    private Map<String, String> params;

    public RegisterRequest(String name, String username, String email, String password, Response.Listener<String> listener){

        super(Method.POST, REGISTER_REQUEST_URL,listener, null);
        params = new HashMap<>();
        params.put("name", name);
        params.put("username", username);
        params.put("email", email);
        params.put("password", password);

    }

    @Override
    public Map<String, String> getParams() {
        return params;
    }
}

<?php
   $con=mysqli_connect("localhost","username","password","dbname");

    $name=$_POST["name"];
    $username = $_POST["username"];
    $email = $_POST["email"];
    $password = $_POST["password"];

    $statement = mysqli_prepare($con, "INSERT INTO user (name, username, email, password) VALUES (?, ?, ?, ?)");
    mysqli_stmt_bind_param($statement, "siss",$name, $username, $email, $password );
    mysqli_stmt_execute($statement);

    $response = array();
    $response["success"] = true;  

    echo json_encode($response);
?>

I know its likely going to be something really stupid but I've been trying to figure this out for two days now.