src/Mail/mime.php
function setHTMLBody($data, $isfile = false)
    {
        if (!$isfile) {
            $this->_htmlbody = $data;
        } else {
            $cont = $this->_file2str($data);
            if ($this->_isError($cont)) {
                return $cont;
            }
            $this->_htmlbody = $cont;
        }

        return true;
    }
function setHTMLBody($data, $isfile = false)
    {
        if (!$isfile) {
            $this->_htmlbody = $data;
        } else {
            $cont = $this->_file2str($data);
            if ($this->_isError($cont)) {
                return $cont;
            }
            $this->_htmlbody = $cont;
        }

        return true;
    }
Adds a html part to the mail.

@param string $data   Either a string or the file name with the
contents
@param bool   $isfile A flag that determines whether $data is a
filename, or a string(false, default)

@return bool          True on success
@access public