Now we can use this class behind a server proxy/firewall

My compagny set a firewall/proxy recently.
I've just made some little change because the exif_imagetype doesn't take care about the proxy configuration like the function file_get_content.

With the change, if the file is a remote one (from an url), we download it with  file_get_content an put it in a temporary file.
When php destroy the class, the temporary file is closed.

And for configure the proxy, i've created a listner who made this : 
[php]
$context = array(
                'http' => array(
                    'proxy' => 'tcp://XXX.XXX.XXX.XXX:8058',
                    'request_fulluri' => true,
                )
            );
stream_context_set_default($this->getStreamContext());
[/php]