function login_user(){
global $con;

if(isset($_POST['submit'])){

    //row dari database
    //get from
    $email = $_POST['email'];
    $email_query=query("SELECT * FROM learn_users WHERE user_email='{$email}'");//sql language
    if(mysqli_num_rows($email_query)==0){
        //mysqli_num_rows akan kira berapa row dalam table itu

        $_SESSION['email_not_valid']=$email;//sebelum redirect tu tambah nih blh masukkan
        redirect("index.php");
    }else{

    $password = escape_string($_POST['password']);

    $query = query ("SELECT * FROM learn_users WHERE user_email = '{$email}' AND user_password = '{$password}'");

    confirm($query);

    while($row = fetch_array($query)){

        $db_user_email = $row['user_email'];
        $db_user_password = $row['user_password'];
        $db_user_role = $row['user_role'];
        $db_username=$row['username'];

    }

    //set the user role, here is user role admin function, klaw user enter punya detail same as database will send the detail to $_session for hold the detail
    if($email == $db_user_email && $password == $db_user_password && $db_user_role == "admin"){

        $_SESSION['user_email'] = $db_user_email;
        $_SESSION['user_role'] = $db_user_role;
        $_SESSION['username']=$db_username;
        //Go to the right page if password and email is correct and user role is admin

        redirect("../admin/index.php");

    }
    if($email == $db_user_email && $password == $db_user_passwor && $db_user_role == "student"){

        $_SESSION['user_email'] = $db_user_email;
        $_SESSION['user_role'] = $db_user_role;
        $_SESSION['username'] = $db_username;

        redirect("../student/index.php");
    }elseif($$email !== $db_username && $password !== $db_user_password){

        redirect("index.php");

    }else{

        //Go to login page if two IF above not satisfied
        redirect("index.php");
    }
}

}

}

function admin_session(){
if(!isset($_SESSION['user_email']) && $_SESSION['user_role']!=='admin'){//session hanya boleh pegang satu account sahaja, untuk pakai remember me (keguaan)}
    //isset mesti ada data

}else{

}
}

function student_session(){
if(isset($_SESSION['user_email']) && $_SESSION['user_role']=='student'){
    //stay in student page

}else{
    redirect("../login/index.php");

}
}

function student_logout(){
unset($_SESSION['user_email']);
unset($_SESSION['user_role']);
unset($_SESSION['username']);

redirect("../login/index.php");
}

function admin_logout(){
unset($_SESSION['user_email']);
unset($_SESSION['user_role']);
unset($_SESSION['username']);

//unset buang data
//Delete all session variables, xkan putar balik
//session_destroy();

//Jump to login page
redirect("../login/index.php");
}

function email_check(){//kalau user berjaya ditambah pakai function tersebut
if(empty($_SESSION['email_not_valid'])){
    //if session is empty, then nt display any data.
}else{
    //if session is not empty, then display message
    ?>
<div class ="alert alert-danger alert-dismissible" role="alert">
<button type="button" class="close" data-dismiss="alert" aria-label="Close">    <span aria-hidden="true">&times;</span></button>
<strong>Strong;</strong><b><?php echo $_SESSION['email_not_valid']?></b>is not registered into this system.
</div>
<?php
        unset($_SESSION['email_not_valid']);
}
}

<?php require MODEL_ROOT . '/admin/functions.php'; ?>

<div class="container">
    <div class="row">
        <div class="col-md-4 col-md-offset-4">
            <div class="login-panel panel panel-default">
                <div class="panel-heading">
                    <h3 class="panel-title">Please Sign In</h3>
                </div>
                <div class="panel-body">
                    <?php
                    email_check();//for email checking purposed
                    ?>

                    <form role="form" action="" method="post">
                        <?php login_user() ?>
                        <fieldset>
                            <div class="form-group">
                                <!--for checking the user have enter email format to this columm, if user enter wrong format, it will have error-->
                                <input class="form-control" placeholder="E-mail" name="email" type="email" autofocus>
                            </div>
                            <div class="form-group">
                                <input class="form-control" placeholder="Password" name="password" type="password" value="">
                            </div>
                            <div class="checkbox">
                                <label>
                                    <input name="remember" type="checkbox" value="Remember Me">Remember Me
                                </label>
                            </div>
                            <!-- Change this to a button or input when using this as a form -->
                            <input type="submit" name="submit" class="btn btn-lg btn-success btn-block" value ="Login">
                            <!--<a href="index.html" class="btn btn-lg btn-success btn-block">Login</a>-->
                        </fieldset>
                    </form>
                </div>
            </div>
        </div>
    </div>
</div>

<?php require MODEL_ROOT . '/admin/functions.php';?>
<?php require VIEW_ROOT . '/templates-student/header.php';

student_session();

?>

 <div id="wrapper">
  <?php require VIEW_ROOT.'/templates-student/navigation.php';?>
    <!-- Page Content -->
    <div id="page-wrapper">
        <div class="container-fluid">
            <div class="row">
                <div class="col-lg-12">
                    <h1 class="page-header">Blank</h1>
                    <?php
                    if($pages_url=="add_subject"){
                        require VIEW_ROOT .  '/templates-admin/form-admin/form_add_subject.php';

                    }elseif($pages_url ==  "no page"){
                        echo "No page displayed";


                    }elseif($pages_url == "logout"){

                        admin_logout();//logout function
                    }elseif($pages_url=="manage_subject"){
                        manage_subject();
                        delete_subject();
                    }elseif($pages_url=="edit_subject"){
                        require VIEW_ROOT . '/templates-admin/form-admin/form_edit_subject.php';
                    }



                    else{

                    }
                    ?>
                </div>
                <!-- /.col-lg-12 -->
            </div>
            <!-- /.row -->
        </div>
        <!-- /.container-fluid -->
    </div>
    <!-- /#page-wrapper -->

</div>
<!-- /#wrapper -->