JAVA JSON RETRIEVER ANDROID

<?php

if (isset($_POST['Username']) && isset($_POST['Password']) && isset($_POST['Database']))
{
    $username = $_POST['Username'];
    $password = $_POST['Password'];
    $database = $_POST['Database'];
    $totalData = array(
        "message" => "",
        "isSuccess" => 0,
        "sesUsername" => $username,
        "sesPassword" => $password,
        "sesDB" => $database
    );
    try
    {
        $db = new PDO('mysql:host=localhost;dbname=user1', 'root', '');
        $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $checkUsers = "SELECT
                        username, password
                    FROM
                        users
                    WHERE
                        username = :username
                    AND
                        password = :password";
        $userStmt = $db->prepare($checkUsers);
        $userStmt->execute(array(
            ':username' => $username,
            ':password' => $password
        ));
        $user = $userStmt->fetchAll();
        $num_rows = count($user);
        if ($num_rows == 1)
        {
            $totalData["success"] = 1;
            $totalData["message"] = "Logged in successfully.";
            echo json_encode($totalData);
        }
        elseif ($num_rows == 0)
        {
            $totalData["success"] = 0;
            $totalData["message"] = "Could not find user. Please check your username and/or password.";
            echo json_encode($totalData);
        }
        else
        {
            $totalData["success"] = 3;
            $totalData["message"] = "No data found. fix your shit.";
            echo json_encode($totalData);
        }
    }

    catch(PDOException $e)
    {
        $message = $e->getMessage();
    }

    $db = NULL;
}