headers

I have a page that users enter their usename and password to login. when they submit their username and password to a MySQL database I want to direct them to a .php page. I want to include their "id" field and have the page check if there is an "id" and if true then it would load the page. If not then it would load the login page again. Thanks in advance for any help. Larry L. webmaster@ldlenterprise.com