Why doesn't my SSI work ?

Answer 1

I've never seen SSI used with PHP in this way so this is something of a long shot, but can you try changing:

AddOutputFilter INCLUDES .php

to:

AddOutputFilterByType INCLUDES text/html

the reason it's not working is that your files no longer have a .php extension (or any extension), since you're routing everything through index.php. The change I've suggested will filter all text/html output (which should include PHP) though the SSI parser, instead of doing so by extension.

Answer 2

Instead of using the SSI include, you could try using the php virtual function:

virtual ("/ssi/test.php?x=hello");

via http://www.zytrax.com/tech/php/php_ssi.htm

What kind of caching requires you to use SSI? Couldn't you just use something like Zend_Cache_Frontend_Output?