On PHPMaster.com today there's a new tutorial that shows you some examples of working with files and the local file system in your PHP applications.

You may well be familiar with databases such as MySQL and Access which are an ever-increasingly common means of storing data. But data is also stored in files, like Word documents, event logs, spreadsheets, image files, and so on. Databases generally require a special query language to retrieve information, whereas files are ‘flat’ and usually appear as a stream of text. [...] PHP provides a range of functions which allow you to work with files, and in this article I’ll demonstrate some of them for you.

Examples in the article include the use of several of the PHP file functions including: filesize, filectime, is_readable, file_put_contents and fopen. There's also an example of using the CSV file functions for working with a comma-separated file (both in reading and writing).