PEAR.php -> PEAR_Error - is it a "bug/misspelling" ?

Hi everybody When trying to understand the concept of error handling I stumbled upon the following inconsistency in PEAR.php in the class PEAR_Error:

        if ($mode & PEAR_ERROR_CALLBACK) {
            $this->level = E_USER_NOTICE;
            $this->callback = $options;
        } else {
            if ($options === null) {
                $options = E_USER_NOTICE;
            }
            $this->level = $options;
            $this->callback = null;
        }
        if ($this->mode & PEAR_ERROR_PRINT) {
            if (is_null($options) || is_int($options)) {
                $format = "%s";
            } else {
                $format = $options;
            }
            printf($format, $this->getMessage());
        }

I'm thinking of these two lines:

        if ($mode & PEAR_ERROR_CALLBACK) {
        if ($this->mode & PEAR_ERROR_PRINT) {

How come one is "$mode" and the other is "$this->mode" ? It shouldn't make any difference but it just seems strange to me with this inconsistency! Cheers, Tommy