php to make login and logout page

<?php 
session_start();

if ($_SESSION['login'] == '1'){
	echo 'U bent ingelogd';
}

if (!isset($_SESSION['login']) || $_SESSION['login'] == '0') { //als er nog geen sessie is of hij is aan 0 / uitgelogd
	if ($_POST['submit']=='Login'){
		$query = "SELECT * FROM `users` WHERE `user` = '{$_POST['loginUser']}'";
		$login = mysql_query($query);
		$dbarray = mysql_fetch_array($login);
		$password = stripslashes($dbarray['password']);
		if ($_POST['loginPass'] == $password) { 
			$_SESSION['login'] = '1';// we maken 1 session aan..
			header('location:');
		}
	}
	?>
	<form action='' method=POST>
	<input type='text' name='loginUser' value=''>
	<input type='text' name='loginPass' value=''>
	<input type='submit' name='submit' value='Login'>
	</form>
	<?php
}
?>

<?php 
session_start(); 

if (isset($_SESSION['login'])) { //als er een sessie is en hij is 1

	if($_SESSION['login'] == '1') { 
		// we maken 1 session aan..
		$_SESSION['login'] = '0';
		echo "U bent nu uitgelogd.";
	}
	else {
		echo "U was al uitgelogd.";
	}

}
?>