Symfony\Component\CssSelector\Tokenizer::tokenizeEscapedString PHP Method

    protected function tokenizeEscapedString($s, $pos)
    {
        $quote = $s[$pos];
        $pos = $pos + 1;
        $start = $pos;
        while (1) {
            $next = strpos($s, $quote, $pos);
            if (false === $next) {
                throw new SyntaxError(sprintf('Expected closing %s for string in: %s', $quote, substr($s, $start)));
            }
            $result = substr($s, $start, $next - $start);
            if ('\\' === $result[strlen($result) - 1]) {
                // next quote character is escaped
                $pos = $next + 1;
                continue;
            }
            if (false !== strpos($result, '\\')) {
                $result = $this->unescapeStringLiteral($result);
            }
            return array($result, $next + 1);
        }
    }