src/Valkyrja/HttpMessage/HeaderSecurity.php
public static function isValid(string $value): bool
    {
        // Look for:
        // \n not preceded by \r, OR
        // \r not followed by \n, OR
        // \r\n not followed by space or horizontal tab; these are all CRLF attacks
        if (preg_match("#(?:(?:(?<!\r)\n)|(?:\r(?!\n))|(?:\r\n(?![ \t])))#", $value)) {
            return false;
        }

        // Non-visible, non-whitespace characters
        // 9 === horizontal tab
        // 10 === line feed
        // 13 === carriage return
        // 32-126, 128-254 === visible
        // 127 === DEL (disallowed)
        // 255 === null byte (disallowed)
        if (preg_match('/[^\x09\x0a\x0d\x20-\x7E\x80-\xFE]/', $value)) {
            return false;
        }

        return true;
    }
public static function isValid(string $value): bool
    {
        // Look for:
        // \n not preceded by \r, OR
        // \r not followed by \n, OR
        // \r\n not followed by space or horizontal tab; these are all CRLF attacks
        if (preg_match("#(?:(?:(?<!\r)\n)|(?:\r(?!\n))|(?:\r\n(?![ \t])))#", $value)) {
            return false;
        }

        // Non-visible, non-whitespace characters
        // 9 === horizontal tab
        // 10 === line feed
        // 13 === carriage return
        // 32-126, 128-254 === visible
        // 127 === DEL (disallowed)
        // 255 === null byte (disallowed)
        if (preg_match('/[^\x09\x0a\x0d\x20-\x7E\x80-\xFE]/', $value)) {
            return false;
        }

        return true;
    }
Validate a header value.

Per RFC 7230, only VISIBLE ASCII characters, spaces, and horizontal
tabs are allowed in values; header continuations MUST consist of
a single CRLF sequence followed by a space or horizontal tab.

@see http://en.wikipedia.org/wiki/HTTP_response_splitting

@param string $value

@return bool