As with all dependency validation, true is returned on success, PEAR_Error on failure for required dependencies (and the PEAR installer dependency is required). If the soft, force or ignore-errors options are specified, an array containing the error message will be returned instead.
Either an array of format array('channel' => channelname, 'package' => package) or one of these objects.
Any object with a log() method that matches the signature of PEAR_Common