SSI vs PHP include

Just in CPU and RAM usage...

[setareh]

I have a website with statics page and use php just for including header, footer and sidebars.
My question is what is difference between php include an SSI in resource using? are they same?
How can I find which one takes more resources to parsing? (my website has a lot of pages and I want reduce CPU usage)

[coopster]

You would have to setup your own time studies pertaining to your server and your setup. I'm guessing after you spent all that time doing so you are going to find milliseconds difference. My opinion? Stick with PHP includes and you'll be fine.