Facebook Graph API Workaround: Get a Group's ID from Its URL

From the archive: first published in September 2013 on my old blog, Tux86’s Web Tech Blog. Versions, links and screenshots are from that time.

In this article, I would like to share my solution for getting a Facebook group ID number from the group’s URL.

Right now, this cannot be done with the Facebook Graph API or FQL. I have no idea why such an old issue still hasn’t been fixed by Facebook!

My solution uses a bot that logs in to Facebook, goes to the target group and extracts the group ID from somewhere in the HTML content.

Here is the source code of a working solution based on the PHP cURL library and DOMXPath.

FacebookBot.php

<?php
class FacebookBot {

    public static $HTTP_POST = "http-post";
    public static $HTTP_GET = "http-get";
    private $email;
    private $pass;
    private $uagent = "Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729)";
    private $cookies = "./cookies.txt";

    public function __construct($email, $pass) {
        $this->email = $email;
        $this->pass = $pass;

        touch($this->cookies);
    }

    private static function toFbMobileUrl($url) {
        return str_replace('//www.facebook.', '//m.facebook.', $url);
    }

    private function callUrl($url, $calltype, $data, &$output) {
        try {
            $curl = curl_init();
            curl_setopt($curl, CURLOPT_URL, $url);
            curl_setopt($curl, CURLOPT_TIMEOUT, 30);
            curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1);
            curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1); //return or not output data
            curl_setopt($curl, CURLOPT_ENCODING, "");
            curl_setopt($curl, CURLOPT_COOKIEFILE, $this->cookies);
            curl_setopt($curl, CURLOPT_COOKIEJAR, $this->cookies);
            curl_setopt($curl, CURLOPT_USERAGENT, $this->uagent);

            if ($calltype == self::$HTTP_POST) {
                $tmp = array();
                foreach ($data as $param_key => $param_value) {
                    $tmp[] = "$param_key=$param_value";
                }
                $data_str = implode("&", $tmp);
                curl_setopt($curl, CURLOPT_POST, 1);
                curl_setopt($curl, CURLOPT_POSTFIELDS, $data_str);
            }
            $output = curl_exec($curl);
            curl_close($curl);
            unset($curl);
        } catch (Exception $e) {
            echo $e->getMessage();
        }
    }

    public function login() {
        $url = "https://m.facebook.com/login.php";
        $post_data = array();
        $post_data['email'] = $this->email;
        $post_data['pass'] = $this->pass;
        $this->callUrl($url, self::$HTTP_POST, $post_data, $output);
    }

    public function logout() {
        $this->callUrl("https://m.facebook.com/", self::$HTTP_GET, null, $html);

        $dom = new DOMDocument;
        @$dom->loadxml($html);
        $links = $dom->getElementsByTagName('a');
        foreach ($links as $link) {
            if (strpos($link->getAttribute('href'), 'logout.php')) {
                $logout = $link->getAttribute('href');
                break;
            }
        }
        $url = 'https://m.facebook.com' . $logout;
        $this->callUrl($url, self::$HTTP_GET, null, $html);
    }

    public function destroyCookies() {
        unlink($this->cookies);
    }

    public function getGroupIdByUrl($url) {
        try {
            $this->callUrl(self::toFbMobileUrl($url), self::$HTTP_GET, null, $html);
            $dom = new DOMDocument;
            @$dom->loadHTML($html);
            $xpath = new DOMXpath($dom);
            $elements = $xpath->query("//a[starts-with(@href, '/groups/')]");
            if ($elements->length > 0) {
                $element = $elements->item(0);
                preg_match("/([0-9]+)/", $element->getAttribute('href'), $matches);
            } else {
                throw new Exception("could not find group id", 1);
            }
            return $matches[0];
        } catch (Exception $e) {
            throw $e;
        }
    }

}

GetGroupIdFromUrl.php

<?php

$group_url=<a facebook group url>;
$email=<your facebook login>;
$pass=<your facebook password>;

try {
    include_once './FacebookBot.php';
    $fbbot = new FacebookBot($email, $pass);
    $fbbot->login();
    $gid = $fbbot->getGroupIdByUrl($group_url);
    $fbbot->logout();
    $fbbot->destroyCookies();
    echo "Group id: ".$gid;
} catch (Exception $e) {
    die("An error has been occurred !");
}

If you find a bug or have an alternative solution, please don’t hesitate to let me know. Thank you.