Search engine PHP?

Hi
I need to setup a search box on my every html page that can search my site within my site from database. I able to make the search box and put it in my site., but I cant find a php script to proscess this. I found many open source scripts but complicated one or I am new to coding. Could someone guide me to a free source for personal and comercial use as well easy to implement?. I have tryed many not able to make it work.

Regards