How do I get curl to correctly identify mime type?

Question

I'm using php to post an image along with some other data.

Using the sample code from the php doc site (example 2 here: http://php.net/manual/en/function.curl-setopt.php, if I output what gets sent with my script ($_FILE) I see something like this:

Array
(
[file] => Array
    (
        [name] => temp.gif
        [type] => application/octet-stream
        [tmp_name] => /tmp/phpO1cgxW
        [error] => 0
        [size] => 3386
    )

) 

My code for creating the post data is:

  $postData = array('sphotos'=>'', 'title'=>urlencode($title), 'description'=>urlencode($description), 'tags'=>$tags, 'category'=>$category, 'gallery'=>'',
    'file'=>'@/web/sites/flickr/temp.gif'); 

I've verified that the file is, in fact, a gif file using the 'file' command in linux.

I just can't get it to show up as a gif type.

Any ideas?

G-Man