mysql real escape string and Cookies

Question

Is there any reason this is bad form? The only user input data on the page is

// Set username and password from cookies
    $username = mysql_real_escape_string($_COOKIE["username"]);
    $password = mysql_real_escape_string($_COOKIE['password']);

I am REALLY new to the idea of sanitizing. Is there any reason this is a terrible way of doing things?

Answer 1

NEVER, EVER store users' data in cookies!

Here's what I suggest:

• store user's ID in cookie
• generate special token and hash+salt and store them in cookies
• store everything in database
• get data from cookies on every page load and try searching for them in database
• if not found, then logout a user
• change token on every page load