PHP Authentication script

I need an authentication script to allow for three of my most important customers to have access to certain documents on my site. I want customers to be directed to and be able to access their folder by entering their email address in one login page, however, only the domain name portion of the email address needs to be authenticated. Depending on their domain name they will be directed to their appropriate folder. For example, if ABC company's email domain is [login to view URL], then an employee of this company can enter his email address in the authentication box on the login page and the script will see that an employee of [login to view URL] is requesting access and it will direct him to the folder for his company. If DEF company's email domain is [login to view URL], then an employee of this company can enter her email address in the authentication box on the login page and the script will see that an employee of [login to view URL] is requesting access and it will direct her to the folder for her company. GHI company employees would be directed to their folder. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). 4) I need an authentication script to allow for three of my most important customers to have access to certain documents on my site. I'll call the companies ABC, DEF and GHI company. I want customers to be directed to and be able to access their folder by entering their email address in one login page, however, only the domain name portion of the email address needs to be authenticated. Depending on their domain name they will be directed to their appropriate folder. For example, if ABC company's email domain is [login to view URL], then an employee of this company named Fred Jones can enter his email address in the authentication box on the login page and the script will see that an employee at [login to view URL] is requesting access and it will direct him to the folder named "abc". If DEF company's email domain is [login to view URL], then an employee of this company named Jane Austin can enter her email address in the authentication box on the login page and the script will see that an employee at [login to view URL] is requesting access and it will direct her to the folder named "def". GHI company employees would be directed to their folder. 5) I need the ability to define the folder names that I will use in the login script myself and to associate them with the appropriate domain name, to change the domain names used in the authentication process, and the ability to add up to five domain names and company folders for later use. 6) If a person enters their email address and the domain name is not in the list of authorized domain names in the login script, I need the script to display an error message that I can configure. 7) The final function that I need is to make sure the ABC company can't see the files inside DEF and GHI's folders. I need the pages in each folder to check to make sure the person has the correct credentials for that particular folder before displaying the page. If ABC's employee has successfully authenticated himself/herself in their particular folder, and if they were to know about the folder names of the other companies and were to try and switch to view those folders, they would fail - an error would pop up telling them that they're not authorized to view the page. 7) All scripts to be written to be compatible with PHP4. ## Platform Operating System: Redhat Linux PHP version: 4.x