it would be helpful to know for sure whether PEAR_Frontend_CLI::displayError() accepts both strings and objects (a little @param string|object in a docblock would be helpful here).

In any case, if you do pear info blah there is a call to a non-object because the source which is:

    function displayError($eobj)
    {
        return $this->_displayLine($eobj->getMessage());
    }

should be:

    /**
     * @param string Error Message
     */
    function displayError($eobj)
    {
        return $this->_displayLine($eobj);
    }

or:

    /**
     * @param object|string either an error message
     *        or a class with a getMessage() method
     */
    function displayError($eobj)
    {
        if (is_object($eobj) {
            return $this->_displayLine($eobj->getMessage());
        } else {
            return $this->_displayLine($eobj);
        }
    }

    }