If you use PHP and you don't have access to a database, or if you need to use a flat file in your application, the Creative Clans File System (CCFS) might be just the thing for you. The CCFS is a class written in PHP to manage the access to flat files in a threadsafe way. On top of that, it also allows you to manipulate the data in the files in a much more sophisticated way than the standard PHP filesystem functions. You can create a definition for each file, use autoincremental values, timestamps, select the fields you want to operate on, select/update/delete only the rows you choose, sort the data. It only requires PHP version 5.x or higher, and it's real easy to install. Just get the latest version from the download section and unzip everything in the root directory of your application.