do i need to explicitly say im using it?

Hi, I am relatively new to programming/networking so I just have a simple question. Once pear packages are installed on the server, do i need to explicitly say in my php code that i am using Pear code? Or will the pear packages be read by php automatically? I know the server has pear enabled because another project was used using it, but I am unsure wether include or require php functions are needed in order to use the Pear functions. Thanks in advance -- Robert Christie