000webhost "0" value at username - android-studio

Question

I connected my android studio program to a database with a login and register function.
Everytime I register my profile the username value is always "0" in the database.
Here's the code:
Register Activity
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
final EditText etAge = (EditText) findViewById(R.id.etAge);
final EditText etName = (EditText) findViewById(R.id.etName);
final EditText etUsername = (EditText) findViewById(R.id.etUsername);
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 password = etPassword.getText().toString();
final int age = Integer.parseInt(etAge.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, MainActivity.class);
RegisterActivity.this.startActivity(intent);
} else {
AlertDialog.Builder builder = new AlertDialog.Builder(RegisterActivity.this);
builder.setMessage("Register Failed")
.setNegativeButton("Retry", null)
.create()
.show();
}
} catch (JSONException e) {
e.printStackTrace();
}
}
};
RegisterRequest registerRequest = new RegisterRequest(name, username, age, password, responseListener);
RequestQueue queue = Volley.newRequestQueue(RegisterActivity.this);
queue.add(registerRequest);
}
});
}
}
Register Request
public class RegisterRequest extends StringRequest{
private static final String REGISTER_REQUEST_URL = "http://animotradings.000webhostapp.com/Register.php";
private Map<String, String> params;
public RegisterRequest(String name, String username, int age, 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("password", password);
params.put("age", age + "");
}
#Override
public Map<String, String> getParams() {
return params;
}
}
Register.php File
<?php
$con = mysqli_connect("localhost", "id52837_animotradings", "password", "id52837_animotradings");
$name = $_POST["name"];
$username = $_POST["username"];
$age = $_POST["age"];
$password = $_POST["password"];
$statement = mysqli_prepare($con, "INSERT INTO user (name, username, age, password) VALUES (?, ?, ?, ?)");
mysqli_stmt_bind_param($statement, "siss", $name, $username, $age, $password);
mysqli_stmt_execute($statement);
$response = array();
$response["success"] = true;
echo json_encode($response);?>