Why do you need to use PHP to login? If it's simply to authenticate users against a MySQL database as opposed to a .htpasswd file, then you might consider something like mod_auth_mysql instead of a PHP form.
Otherwise, I would agree with laserlight in simply writing a PHP script that handles the authentication/directory listing/file downloads.
Xager wrote:The main reason for wanting to keep .htaccess is that i would need to create about 5 more pages and when you're alone and not that familiar with php that's not an easy task
Quite incorrect - I use the exact same method described by laserlight; a PHP page presents users with a login form, validates their credentials against a MySQL DB, lists the files available to them in a certain directory, and sends them whichever file they click on. All of this is done through one single .php file.
It's just a matter of putting together some simple topics with one or two that you might not be familiar with, such as using [man]glob/man to retrieve a list of files in a directory and then [man]readfile/man plus the appropriate [man]header/man's to send whichever file they clicked on.