Hi akacj,
Its not that hard as you think. Here`s some sample code to get you started,
$sql = "SELECT id FROM users WHERE username = '".mysql_escape_string($_POST['email'])."' AND password = '".md5($_POST['pass'])."'";
$row = mysql_query($sql);
if(mysql_num_rows($row) > 0)
{
//register session
//redirect user to member page
header("Location: member.php");
}
else
//Error invalid user name or password
P.S: this is just an sample code please make sure to do the necessary changes as according to your application.
since your validation all the inputs in form_process.php page make sure to have this code on top of that page.
Hope this clear your doubts,
Best regards,
Niroshan