PHP Password Protect Your Web Pages
Click on sas.zip to download the GNU GENERAL PUBLIC LICENSE script.
Quoting the author, www.zann-marketing.com,
Simple Authorization Script, or SAS, is a php script which allows web pages to be password protected without the use of a database. It’s simple to install and simple to use. Simple Authorization Script uses php and cookies to password protect web pages. It doesn’t require a username to access the page, only a password.
You will find the installation instructions in the zip file.