The PEAR package contains:
* the PEAR installer, for creating, distributing and installing packages
* the PEAR_Exception PHP5 error handling mechanism
* the PEAR_ErrorStack advanced error handling mechanism
* the PEAR_Error error handling mechanism
* the OS_Guess class for retrieving info about the OS where PHP is running on
* the System class for quick handling of common operations with files and
  directories
* the PEAR base class