enigma1 - 12:09 pm on Apr 22, 2011 (gmt 0)

The php ob_start switches buffering on. Using ob_start("ob_gzhandler") may cause problems if you're caching content with a 304 header as in these cases no content will be sent by the server but because of the ob_gzhandler the browser may think the content is corrupt. Best to use the default ob_start() and then gzip the buffer.

these AV companies believe that it will bog down your CPU uncompressing everything before doing on-the-fly AV checking (charitable explanation) or are too damn lazy to design their programs right (my explanation).

Which is unfortunate but the same happens with various proxies isps deploy to send all resources as compressed content the the client breaking js and css and making pages unreadable. I wouldn't workaround breaking the http spec by sending cookies. Let them fix their code.