lib/Middleware/Cookie/Cookie.php
public function matchesDomain(string $domain): bool
    {
        $cookieDomain = $this->getAttribute(static::ATTR_DOMAIN) ?? '';

        if (0 === strpos($cookieDomain, '.')) {
            $pattern = '/\b'.preg_quote(substr($cookieDomain, 1), '/').'$/i';

            return (bool) preg_match($pattern, $domain);
        } else {
            return 0 == strcasecmp($cookieDomain, $domain);
        }
    }
public function matchesDomain(string $domain): bool
    {
        $cookieDomain = $this->getAttribute(static::ATTR_DOMAIN) ?? '';

        if (0 === strpos($cookieDomain, '.')) {
            $pattern = '/\b'.preg_quote(substr($cookieDomain, 1), '/').'$/i';

            return (bool) preg_match($pattern, $domain);
        } else {
            return 0 == strcasecmp($cookieDomain, $domain);
        }
    }
Returns true if the current cookie matches the supplied domain.

@param string $domain A domain hostname