PHPMailer::encodeQ( string $str, string $position = 'text' ): string

3698    public function encodeQ($str, $position = 'text')3699    {3700        //There should not be any EOL in the string3701        $pattern = '';3702        $encoded = str_replace(["\r", "\n"], '', $str);3703        switch (strtolower($position)) {3704            case 'phrase':3705                //RFC 2047 section 5.33706                $pattern = '^A-Za-z0-9!*+\/ -';3707                break;3708            /*3709             * RFC 2047 section 5.2.3710             * Build $pattern without including delimiters and []3711             */3712            /* @noinspection PhpMissingBreakStatementInspection */3713            case 'comment':3714                $pattern = '\(\)"';3715            /* Intentional fall through */3716            case 'text':3717            default:3718                //RFC 2047 section 5.13719                //Replace every high ascii, control, =, ? and _ characters3720                $pattern = '\000-\011\013\014\016-\037\075\077\137\177-\377' . $pattern;3721                break;3722        }3723        $matches = [];3724        if (preg_match_all("/[{$pattern}]/", $encoded, $matches)) {3725            //If the string contains an '=', make sure it's the first thing we replace3726            //so as to avoid double-encoding3727            $eqkey = array_search('=', $matches[0], true);3728            if (false !== $eqkey) {3729                unset($matches[0][$eqkey]);3730                array_unshift($matches[0], '=');3731            }3732            foreach (array_unique($matches[0]) as $char) {3733                $encoded = str_replace($char, '=' . sprintf('%02X', ord($char)), $encoded);3734            }3735        }3736        //Replace spaces with _ (more readable than =20)3737        //RFC 2047 section 4.2(2)3738        return str_replace(' ', '_', $encoded);3739    }