demo/assets/php/login.php

<?php

if(!empty($_POST['enter'])){
    $sql = 'SELECT * FROM `users` WHERE 
    `login`=:login AND
    `password` = :password';
    $sth = $dbh->prepare($sql, [PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY]);
    $sth->execute([
        "login"=>$_POST['login'],
        "password"=>$_POST['password']
    ]);
    $red = $sth->fetch();
    if($red){
        setcookie("id", $red['id_user'], time()+3600);
        setcookie("role", $red['role'], time()+3600);
        header('Location: order.php');
    }else{
        echo "<script>alert('Неверный логин или пароль');</script>";
    }
}

?>