How about you tell us what the error message says, and then post your login script here?

It really depends on what you are trying to do...

Do you want a login script, which simply blocks access for unauthorized use? Or do you need a "membership" script with various usernames and user priviliges?

If you simply need want to block access to your website, you will be very happy with this script. I am using it all the time when I would like to block access.

If you are looking for a membership site, check out amember.

And additionally, there is the most simple way: add a pw to a dir via your cpanel (or manually create a .htaccess file). (find out more)

I recommend you to write script yourself. This way you can be 100% sure that there are no exploits available - and it would be harder to brake your protection. Of course you should write it well to make it protected from hackers.

Regarding the error - tell us what is it and we'll try to help you with it.

Not sure what you are trying to do but I agree don't try to reinvent the wheel. Try using wordpress with s2 members plugin works great for me. Also Joomla has some extentions that work to.

If you are just trying to learn PHP and MySQL, learning by trail and error is the best way.