login script

I need to make a login script that uses a text document as its database to hold all their passwords and usernames so wen they go to login the page reas from the document and gt the usernam and the password and if the username and password is not the same as the on in the document then it will not log in and wen ever the user logs in they can edit their profile and if their the admin they can edit/delet everyones profile is this posssible and if so could you please give me an example of how the script is made thanks (to who ever replies)