src/Mail/mime.php
function &_addAlternativePart(&$obj = null)
    {
        $params['content_type'] = 'multipart/alternative';
        $params['eol']          = $this->_build_params['eol'];

        if (is_object($obj)) {
            $ret = $obj->addSubpart('', $params);
        } else {
            $ret = new Mail_mimePart('', $params);
        }

        return $ret;
    }
function &_addAlternativePart(&$obj = null)
    {
        $params['content_type'] = 'multipart/alternative';
        $params['eol']          = $this->_build_params['eol'];

        if (is_object($obj)) {
            $ret = $obj->addSubpart('', $params);
        } else {
            $ret = new Mail_mimePart('', $params);
        }

        return $ret;
    }
Adds a multipart/alternative part to a mimePart
object (or creates one), and returns it during
the build process.

@param mixed &$obj The object to add the part to, or
null if a new object is to be created.

@return object     The multipart/mixed mimePart object
@access private