login.php

<?php
        include('dbcon.php');
        session_start();
        $username = $_POST['username'];
        $password = $_POST['password'];

        /* admin */
        $resultFilms = $conn->prepare("select * from users where username = '$username' and password = '$password'")or die(mysql_error());
        $resultFilms->execute();
        $num_row = $resultFilms->rowcount();
        $row = $resultFilms->fetch();

        /* Staff */
        $query_teacher = $conn->prepare("SELECT * FROM staff WHERE username='$username' AND password='$password'")or die(mysql_error());
        $query_teacher->execute();
        $num_row_teacher = $query_teacher->rowcount();
        $row_teahcer = $query_teacher->fetch();



        if( $num_row > 0 ) {
        $_SESSION['id']=$row['user_id'];
        echo 'true_user';
        $conn->query("insert into user_log (username,login_date,user_id)values('$username',NOW(),".$row['user_id'].")")or die(mysql_error());
        }
        else if ($num_row_teacher > 0){
        $_SESSION['id']=$row_teahcer['staff_id'];
        echo 'true';
        $conn->query("insert into user_log (username,login_date,user_id)values('$username',NOW(),".$row_teahcer['staff_id'].")")or die(mysql_error());
         }

         else{
                echo 'false';
        }
        ?>