Some more stuff that belongs in a wiki. These are some notes on PEAR, the PHP Extension and Application Repository.
PEAR is most useful when a required php module, or a current enough version of a module, isn’t available in your distribution’s package repository. Modules in the PECL (PHP Extension Community Library) repository can also be installed and managed using the pear utility.
To find all PEAR modules installed on your system:
What version of pear?
All the above require the name of a module as an argument.
Find the path where modules are installed:
pear config-get php_dir
For more see the PEAR Manual.