The functions in this 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.
This extension is derivated from Apache mod_mime_magic, which is itself based on the file command maintaind by Ian F. Darwin. See the source code for further historic and copyright information.
You must compile PHP with the configure switch --enable-mime-magic to get support for mime-type functions. The extension needs a copy of the magic.mime as distributed with the file command. This file also part of most recent Linux distributions and usually stored in the /usr/share/misc directory.
The behaviour of these functions is affected by settings in php.ini.
Table 1. Mimetype configuration options