Website help for login

Im already have a android app connected to my database so that it logs in i need to do the same for a website but im am having trouble.

I cant seem to get it to work

Im using php my admin for the databases.

Is there a away to connect both the app and the website so users can log in. I have not been able to successfully so far.

    Connection.php
      <?php
   define('DB_SERVER', 'localhost:3036');
      define('DB_USERNAME', 'root');
   define('DB_PASSWORD', 'rootpassword');
   define('DB_DATABASE', 'database');
   $db = mysqli_connect(DB_SERVER,DB_USERNAME,DB_PASSWORD,DB_DATABASE);
 ?>


  logingpage.php

  <?php
  include("connection.php");
  session_start();

    if($_SERVER["REQUEST_METHOD"] == "POST") {


     $username = mysqli_real_escape_string($db,$_POST['username']);
     $password = mysqli_real_escape_string($db,$_POST['password']); 
     $sql = "SELECT id FROM user WHERE username = '$username' and     
     passcode'$password'"; 


     $result = mysqli_query($db,$sql);
     $row = mysqli_fetch_array($result,MYSQLI_ASSOC);
     $active = $row['active'];

     $count = mysqli_num_rows($result);


     if($count == 1) {
        session("username");
       $_SESSION['login_user'] = $username;

      header("location: Logged_In.php");
        }else {
                $error = "Login Incorrect";
       }
    }
 ?>