1and1 gives us PHP out of the box, but not necessarily all the standard PHP extensions. This document shows you how to add standard PHP extensions (PEAR modules) to the default setup. You can read more about PEAR at the PEAR homepage.
Creating the .pearrc config file
For PEAR to work, you'll need to create a config file. This has already been done on the current server at:
/kunden/homepages/43/d109612362/htdocs/.pearrc
If you need to recreate this file for whatever reason, log in via SSH and run:
pear config-create /kunden/homepages/43/d109612362/htdocs/ .pearrc
Note the space between the path and the filename. config-create in fact takes two arguments. Also, you may want to chmod 600 the file to prevent any web access.
Create the PEAR directory structure in home dir
(This has already been done on the current server.)
pear install -o PEAR
Install PEAR modules
From here, everything should work. You can use normal PEAR commands to install packages. Normally, you'll only do this:
pear install Package_Name