The functions in the fileinfo module try to guess the content type and encoding of a file by looking for certain magic byte sequences at specific positions within the file. While this is not a bullet proof approach, the heuristics used do a very good job.
You can find more information about fileinfo at php.net – File Information.
This module is enabled by default on all DreamHost accounts. You can confirm by adding a phpinfo.php file to your website. View the following article for instructions on how to add this file:
After it's been created, view the following URL in your browser:
- You should see the following in the page that appears: