cURL retrieve only URL address - php

Question

Using PHP and cURL, I'd like to check if I can login to a website using the provided user credentials. For that I'm currently retrieving the entire website and then use regex to filter for keywords that might indicate the login didn't work.
The url itself contains the string "errormessage" if a wrong username/password has been entered. Is it possible to only use curl to get the url address, without the contents to speed it up?
Here's my curl PHP code:
function curl_get_request($referer, $submit_url, $ch)
{
global $cookie_path;
// sends a request via curl to the string specifics listed
$agent = "Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax)";
curl_setopt($ch, CURLOPT_URL, $submit_url);
curl_setopt($ch, CURLOPT_USERAGENT, $agent);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_REFERER, $referer);
curl_setopt($ch, CURLOPT_COOKIEFILE, $cookie_path);
curl_setopt($ch, CURLOPT_COOKIEJAR, $cookie_path);
return $result = curl_exec ($ch);
}
Also, if somebody has a better idea on how to handle a problem like this, please let me know!

Answer 1

What you should do is check the URL each time there is a redirect. Most redirects are going to be done with the proper HTTP headers. If that is the case, see this answer:
PHP: cURL and keep track of all redirections
Basically, turn off automatic redirection following, and check the HTTP status code for 301 or 302. If you get one of those, you can continue to follow the redirection if needed, or exit from there.
If instead, the redirection is happening client side, you will have to parse the page with a DOM parser.