public function encodeHeader($str, $position = 'text')
    {
        $matchcount = 0;
        switch (strtolower($position)) {
            case 'phrase':
                if (!preg_match('/[\200-\377]/', $str)) {
                    // Can't use addslashes as we don't know the value of magic_quotes_sybase
                    $encoded = addcslashes($str, "\0..\37\177\\\"");
                    if (($str == $encoded) && !preg_match('/[^A-Za-z0-9!#$%&\'*+\/=?^_`{|}~ -]/', $str)) {
                        return ($encoded);
                    } else {
                        return ("\"$encoded\"");
                    }
                }
                $matchcount = preg_match_all('/[^\040\041\043-\133\135-\176]/', $str, $matches);
                break;
            /** @noinspection PhpMissingBreakStatementInspection */
            case 'comment':
                $matchcount = preg_match_all('/[()"]/', $str, $matches);
            // Intentional fall-through
            case 'text':
            default:
                $matchcount += preg_match_all('/[\000-\010\013\014\016-\037\177-\377]/', $str, $matches);
                break;
        }

        if ($matchcount == 0) { // There are no chars that need encoding
            return ($str);
        }

        $maxlen = 75 - 7 - strlen($this->CharSet);
        // Try to select the encoding which should produce the shortest output
        if ($matchcount > strlen($str) / 3) {
            // More than a third of the content will need encoding, so B encoding will be most efficient
            $encoding = 'B';
            if (function_exists('mb_strlen') && $this->hasMultiBytes($str)) {
                // Use a custom function which correctly encodes and wraps long
                // multibyte strings without breaking lines within a character
                $encoded = $this->base64EncodeWrapMB($str, "\n");
            } else {
                $encoded = base64_encode($str);
                $maxlen -= $maxlen % 4;
                $encoded = trim(chunk_split($encoded, $maxlen, "\n"));
            }
        } else {
            $encoding = 'Q';
            $encoded = $this->encodeQ($str, $position);
            $encoded = $this->wrapText($encoded, $maxlen, true);
            $encoded = str_replace('=' . self::CRLF, "\n", trim($encoded));
        }

        $encoded = preg_replace('/^(.*)$/m', ' =?' . $this->CharSet . "?$encoding?\\1?=", $encoded);
        $encoded = trim(str_replace("\n", $this->LE, $encoded));

        return $encoded;
    }