The TutsPlus.com site has a new tutorial posted with an introductory level tutorial showing how to upload files with PHP and some example code to illustrate the process.

In this article, I’ll explain the basics of file upload in PHP. Firstly, we’ll go through the PHP configuration options that need to be in place for successful file uploads. Following that, we’ll develop a real-world example of how to upload a file.

The starts with the settings you'll need to update in your php.ini file for the temporary storage directory, the max file size, maximum post size and several others. They explain what each of the settings is for an suggest values you can use for most upload situations. They then move on to the code, showing the HTML to create the upload form and the PHP to handle the form submission. They also add in some filename sanitization and file extension restrictions.