PHP is spesific to a file. You could add some authentication to each php file in the folder, or to actually password the entire folder, you would need to setup an apache htaccess file

The server can be set to not show directories at all (that’s usually the default), so you’d have to use php to show the directory. Then you just don’t show the directories you want not showed.

yes but you have to use a database then use in the html

you can create a simple login script with mysql or a flat file. If php is installed on apache then you can use .htaccess. below are some examples.

For what I read, I think what Dsfasdf A is looking for is a way for a script to create a password protected directory on the fly. It can be made, if the script first creates a directory, and then creates two text files inside named .htaccess and .htpasswd and write to them the configuration options.