index.php:
<h1>Login</h1>
<form id='login' action='loginscript.php' method='post'>
	<div>Username:</div>
	<div><input type='text' name='username'/></div>
	<div>Password:</div>
	<div><input type='password' name='password'/></div>
	<div><input type='submit' name='submit' value='Login'/></div>
</form>

loginscript.php:
$user = $_POST['username'];
$pass = $_POST['password'];

echo "Logged in as $user/$pass"