The @filesource tag can only be used in a page-level DocBlock, it will be ignored anywhere else. phpDocumentor parses the file source of the current file, and outputs syntax-highlighted source code with line numbers, links to documentation and then adds a link to the generated file in the documentation.
The @example tag serves a similar purpose, but is designed to parse and create a link to an external example file.@filesource only works with PHP 4.3.0+ due to the use of the tokenizer extension, which was not stable prior to PHP 4.3.0. Go to http://www.php.net and download PHP 4.3.0 to use @filesource
Here's an example: