<?php include 'db_connection.php';
     session_start();
    if(isset($_POST['login'])){
       if(!empty($_POST['username']) && !empty($_POST['password']){
             $get_username=mysqli_real_escape_string($conn,$_POST['username'];
             $get_password=mysqli_escape_string($conn,$_POST['password'];
          $sql = "SELECT * FROM EMPLOYEES WHERE EMP_USERNAME = '$get_username' AND EMP_PASSWORD = '$get_password'");
            if($result = mysqli_query($conn,$sql)){
                if(mysqli_num_rows($result) == 1{
                   $_SESSION['username'] = $get_username;
                   $_SESSION['password'] = $get_password;
                   header("Location:../index.php");
                }else{
                    header("Location:../index.php?login=wrong");
                }
         }else{
              header("Location:../index.php?login_error=query_error");
         }
       }else{
            header("Location:../index.php?login_error=login_empty");
       }
    }

<?php
   $servername = "localhost";
   $username = "root";
   $password= "";
   $dbname = users;

   $conn = new mysqli($servername, $username,$password,$dbname);
    if($conn->connect_error){
       die("connection failed: ".$conn->connect_error);
    }
?>