You must compile PHP with the configure switch
--with-mime-magic to get support for
mime-type functions. The extension needs a copy of the simplified
magic file that is distributed with the Apache httpd.
The configure option has been changed from
to --with-mime-magic since PHP 4.3.2
This extension is not capable of handling the fully decorated
magic file that generally comes with
standard Linux distro's and is supposed to be used with
recent versions of file command.
Note to Win32 Users
In order to use this module on a Windows environment, you must set the path
to the bundled magic.mime file in your php.ini.