The uninstall command removes a package and accepts a list of installed packages to remove as arguments.
Plugins (documented here) must be explicitly uninstalled with the -p or --plugin option. Plugins are installed into the location specified by the plugins_dir configuration variable, which defaults to the same location that the user configuration file is located ($HOME/.pear in unix, <My Documents>\pear on windows).
php pyrus.phar uninstall -p PEAR2_Pyrus_Developer
The --force or -f option can be used to force uninstallation if there are errors. For instance, this can be used to override problems in dependency validation. As such, it should be used sparingly if at all. Better is to uninstall the packages tha depend on the package being uninstalled.