Detecting Pear....

I would like to use Pear for a project I am making for someone else, but it will be distributed in a way where people might not be able to install Pear on their machines. So I was thinking of simply including the classes I need with the archive I will give them. So somehow I need to be able to detect if Pear is in their inlcude path and if not then include it with the one that I will have in my distriubution. What would be the best way to detect if pear is installed and in the persons include path already? Thanks, Mike