Newbie: Running scripts

[Anon]

I've just started on PHP after designing a site where SSI wasn't enough anymore and have a couple of questions:

I understand you can't use SSI and PHP on the same page so how do you run Perl scripts with PHP?

Does virtual() put less stress on the server than include() ?

If I make a page with SSI and use a virtual include to include a PHP page will the included data be the raw text from the PHP file, or will the server run the
PHP first and include the output of that in the SSI page? Am I right in thinking this would allow me to have pages with a .shtml extension that are really the result of PHP?

The server is Apache 1.3.3 on FreeBSD if that matters.

TIA

[Anon]

You can use the passthru() function as described in the manual.
That executes a shell command (can be a perl script)
and passes all the output to the browser, much like SSI would.