PNG files on MediaWiki

On some installs of MediaWiki, PNG images will not upload correctly. This occurs because the MIME type of the image is not being read correctly - MediaWiki is interpreting them as text/plain when in fact they should be being interpreted as image/png. If your MediaWiki install has this problem, a simple solution to it would be to add the following line to the end of your LocalSettings.php file in the root of the wiki install:

$wgMimeDetectorCommand= "file -bi";