PHP Cloudflare Resolver

<?php
/** Cloudflare Resolver **
 */
interface ICFlareResolver {
    public function resolve_cf($url);
    public function isValidIp($ip);
    public function isValidUrl($url);
    public function isCloudFlare($host);
}

class CFlareResolver implements ICFlareResolver {
    private $_addr_alloc = array(
                '199.27.128.0/21',
                '173.245.48.0/20',
                '103.21.244.0/22',
                '103.22.200.0/22',
                '103.31.4.0/22',
                '141.101.64.0/18',
                '108.162.192.0/18',
                '190.93.240.0/20',
                '188.114.96.0/20',
                '197.234.240.0/22',
                '198.41.128.0/17',
                '162.158.0.0/15',
                '104.16.0.0/12',
                '172.64.0.0/13'
            );

    private $_subd_alloc = array(
                'mail',
                'direct',
                'direct-connect',
                'cpanel',
                'ftp',
                'forum',
                'blog',
                'test',
                'dev',
                'webmail',
                'record',
                'homepage',
                'testing',
                'secure',
                'server',
                'news',
                'images',
                'irc',
                'groups',
                'cp',
                'info',
                'games',
                'music',
                'portal',
                'ssl',
                'dns',
                'help',
                'host',
                'www',
                'help',
                'images',
                'news',
                '1'
            );

    public function resolve_cf($url) {
        if(!$this->isValidUrl($url)) {
            $url = "http://{$url}";
        }

        if($this->isCloudFlare($url)) {
            $host = parse_url($url)['host'];
            if(strstr($host, 'www.')) {
                $host = explode('www.', $host)[1];
            }

            foreach($this->_subd_alloc as $subdomain) {
            $host_pre_ = "{$subdomain}.{$host}";
                $host_ip = $this->getIp($host_pre_);
                if($this->isValidIp($host_ip)) {
                    if($this->isCloudFlare($host_ip))
                        echo "{$host_pre_}:::{$host_ip}:::Cloudflare" . (isset($ARGV[0])?"\r\n":"<br>\r\n";
                    else {
                        echo "{$host_pre_}:::{$host_ip}:::DirectIP" . (isset($ARGV[0])?"\r\n":"<br>\r\n";
                    }
                }
            }
        }
    }

    public function isValidIp($ip) {
        return filter_var($ip, FILTER_VALIDATE_IP) ? true : false;
    }

    public function isValidUrl($url) {
        return filter_var($url, FILTER_VALIDATE_URL) ? true : false;
    }

    public function isCloudFlare($host) {
        if($this->isValidIp($host)) {
            foreach($this->_addr_alloc as $addr_alloc) {
                if($this->cidr_match($host, $addr_alloc)) {
                    return true;
                }
            }
            return false;
        }
        elseif($this->isValidUrl($host)) {
            $headers = implode("\n", get_headers($host));
            $headers = explode("cloudflare", $headers);
            return count($headers)>1 ? true : false;
        }
    }

    private function getIp($host)
    {
        return gethostbyname($host);
    }

    private function cidr_match($ip, $range) {
        list ($subnet, $bits) = explode('/', $range);
        $ip = ip2long($ip);
        $subnet = ip2long($subnet);
        $mask = -1 << (32 - $bits);
        $subnet &= $mask; # nb: in case the supplied subnet wasn't correctly aligned
        return ($ip & $mask) == $subnet;
    }

}