The different installer front-ends differ only in their user-interface specific parts; the core, executing part of each command, is shared between all front-ends. Their configuration parameters are also common; the documentation base directory used in the command-line installation is the same one used by the Gtk installer, and so on.
The PEAR Installer has many configuration parameters, only some of which you need to worry about right now. Look at the PEAR main directory parameter and the other directory parameters first.
Next is the complete list of configuration parameters in the PEAR Installer (see Table 10.4). This is close to what you see when running the pear config-show command.