Symfony\Component\CssSelector\Tokenizer::unescapeStringLiteral PHP Метод

    protected function unescapeStringLiteral($literal)
    {
        return preg_replace_callback('#(\\\\(?:[A-Fa-f0-9]{1,6}(?:\\r\\n|\\s)?|[^A-Fa-f0-9]))#', function ($matches) use($literal) {
            if ($matches[0][0] == '\\' && strlen($matches[0]) > 1) {
                $matches[0] = substr($matches[0], 1);
                if (in_array($matches[0][0], array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'a', 'b', 'c', 'd', 'e', 'f'))) {
                    return chr(trim($matches[0]));
                }
            } else {
                throw new SyntaxError(sprintf('Invalid escape sequence %s in string %s', $matches[0], $literal));
            }
        }, $literal);
    }