$error = $login = $parol = "";
if (isset($_POST['login']))
{
$login = $_POST['login'];
$parol = $_POST['parol'];
if ($login == "" || $parol == "")
{
$error = "Not all fields were entered<br />";
}
else
{
$query = $con-> query("SELECT login,parol FROM users
WHERE login='$login' AND parol='$parol'");
if($query->num_rows > 0){
$error = "<span class='error'>Username/Password
invalid</span><br /><br />";
}
else
{
$_SESSION['login'] = $login;
$_SESSION['parol'] = $parol;
header('location: index.php');
}
}
}

<div class="title">Kirish</div>
<div class="menu">
<form action="login.php" method="POST">
Login:<br> <input type="text" name="login"/><br/>
Parol:<br> <input type="password" name="parol"/><br/>
<input type="submit" value="Kirish" class="button"/>
</form>
</div>
<div class="forlink"><a href="/reg" class="links"><img src="/img/reg.png" alt="reg">Registratsiya</a></div>
    <div class="forlink"><a href="/forgot" class="links"><img src="/img/help.png" alt="help">Parolni unutdim?</a></div>