The 4.x releases of PHP add Last-Modified, Pragma, Cache-Control, and Expires headers to the data sent back to the browser.

This is not documented anywyere, and furthermore overrides the default caching setup of a web server. With no function to remove headers, you simply have to change the source, or overwrite all of the headers - which doesn't work in all browsers anyway.

I'm not quite sure why this was done - and don't really like it - since session is either on or off for the entire server.

Perhaps there is a better way to acheive this?