public static function encodeQuotedPrintable($str,
        $lineLength = self::LINELENGTH,
        $lineEnd = self::LINEEND)
    {
        $out = '';
        $str = self::_encodeQuotedPrintable($str);

        // Split encoded text into separate lines
        while ($str) {
            $ptr = strlen($str);
            if ($ptr > $lineLength) {
                $ptr = $lineLength;
            }

            // Ensure we are not splitting across an encoded character
            $pos = strrpos(substr($str, 0, $ptr), '=');
            if ($pos !== false && $pos >= $ptr - 2) {
                $ptr = $pos;
            }

            // Check if there is a space at the end of the line and rewind
            if ($ptr > 0 && $str[$ptr - 1] == ' ') {
                --$ptr;
            }

            // Add string and continue
            $out .= substr($str, 0, $ptr) . '=' . $lineEnd;
            $str = substr($str, $ptr);
        }

        $out = rtrim($out, $lineEnd);
        $out = rtrim($out, '=');
        return $out;
    }