Retrieve file extension according its MIME type

Posted on 2007-03-20
Medium Priority
Last Modified: 2010-08-05
I have files stored as BLOB records in database, with no further information. I want users to be able to download them, so first I save that BLOB to file and then use "system('file -i -b filename')" command to obtain its MIME type. Now I need to retrieve file extention from that MIME type (so that when user downloads the file, his operating system can open it correctly). Any idea how to retrieve it ?
Question by:protein007
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LVL 48

Accepted Solution

hernst42 earned 1500 total points
ID: 18757130
There is no php-function or program which will tell you which ending to use. apache ships a mime.types where the application-types are listed with their possible endings. So read with php the mime.types-file and search of the application-type you got from the file-command and use the first extension in the file. The file looks like:

image/ief ief
image/jpeg jpeg jpg jpe
image/jpeg2000 jp2
image/png png
image/rle rle
LVL 24

Expert Comment

ID: 18757160
If the filename was not stored, I do not believe that there will be an automated way to do this. You will need to associate the extensions with the MIME types as needed. For example:

switch ($mimeType)
   case 'image/jpeg':
      $extension = 'jpg';
   case 'image/bmp':
      $extension = 'bmp';
   case 'application/xml':
      $extension = 'xml';

You will just need to create a case for each potential MIME type stored in your database. You can use http://www.ltsw.se/knbase/internet/mime.htp to retrieve a list of MIME types.
LVL 24

Expert Comment

ID: 18757168
Sorry, hernst42 got there first. I apologize for the cross-post.
LVL 48

Expert Comment

ID: 18757206
It's no cross post, nor its the same solution so let the questioneer decide which solutions fits better for him.

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