What are the ways to detect whether a file is a compressed file, while writing a upload script in PHP?

From what i understand, you need to detect a file of type zip or rar, image/gif would be the mime of a gif file, so you need to look for mime types like: application/zip application/x-rar-compressed A good mime types reference can be found in wikipedia: http://en.wikipedia.org/wiki/Internet_media_type And here: http://www.hansenb.pdx.edu/DMKB/dict/tutorials/mime_typ.php Also, for PHP you might also look into: http://php.net/manual/en/function.mime-content-type.php this function, notice it's part of the Fileinfo package, not always compiled with default PHP. and this PEAR package too: http://pear.php.net/package/MIME_Type

You can check the file type and, if it's a zip file, use http://www.php.net/manual/en/function.zip-read.php to look inside it. Call zip_open() first, then call zip_read() to look at each file in the archive and check its type. I just searched for a similar ability with rar files and found http://www.php.net/manual/en/class.rararchive.php It's setup a little differently, as a class rather than global functions, but appears to be the same idea. I guess the difference is because the zip functions predate OO support in PHP. Also, it looks like this rar functionality may not be in a released version of PHP yet.

You can check the extension of the file and also the MIME type of the file to check whether the file is a compressed file. But dont forget that they can be spoofed easily.

This is tagged under cakePhp. There is an incredibly well written library called http://milesj.me/code/cakephp/uploader which will save the MIME type for you, and you need not do any explicit "uploading" as it is augmented as a behavior and a simple model->save() will save the file (including transporting it to a 3rd party provider like Amazon S3). As mentioned already, use the appropriate MIME to detect the file. extensions are unreliable and can lie. If you want to however detect it at the client-side, before any uploading to the server happens (again not reliable, because a browser can lie) then you can use the html5 http://dev.w3.org/2006/webapi/FileAPI/ to detect it. Again purely using this api means you take a hit on cross browser compatibility.