PHP: Check if URL redirects?

Question

I have implemented a function that runs on each page that I want to restrict from non-logged in users. The function automatically redirects the visitor to the login page in the case of he or she is not logged in.

I would like to make a PHP function that is run from a exernal server and iterates through a number of set URLs (array with URLs that is for each protected site) to see if they are redirected or not. Thereby I could easily make sure if protection is up and running on every page.

How could this be done?

Thanks.

Answer 1

Do you want to check the HTTP code to see if it's a redirect?

    $params = array('http' => array(
        'method' => 'HEAD',
        'ignore_errors' => true
    ));

    $context = stream_context_create($params);
    foreach(array('http://google.com', 'http://stackoverflow.com') as $url) {
      $fp = fopen($url, 'rb', false, $context);
      $result = stream_get_contents($fp);

      if ($result === false) {
          throw new Exception("Could not read data from {$url}");
      } else if (! strstr($http_response_header[0], '301')) {
          // Do something here
      }
    }

Answer 2

function unshorten_url($url){
    $ch = curl_init();

    curl_setopt($ch, CURLOPT_HEADER, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_URL, $url);
    $out = curl_exec($ch);

    $real_url = $url;//default.. (if no redirect)

    if (preg_match("/location: (.*)/i", $out, $redirect))
        $real_url = $redirect[1];

    if (strstr($real_url, "bit.ly"))//the redirect is another shortened url
        $real_url = unshorten_url($real_url);

    return $real_url;
}

Answer 3

I hope it will help you:

function checkRedirect($url)
{
        $headers = get_headers($url);
        if ($headers) {
            if (isset($headers[0])) {
                if ($headers[0] == 'HTTP/1.1 302 Found') {
                    //this is the URL where it's redirecting
                    return str_replace("Location: ", "", $headers[9]);
                }
            }
        }
        return false;
}
$isRedirect = checkRedirect($url);
if(!$isRedirect )
{
   echo "URL Not Redirected";
}else{
   echo "URL Redirected to: ".$isRedirect;
}

Answer 4

I use curl and only take headers, after I compare my url and url from header curl:

                $url="http://google.com";
                $ch = curl_init();

                curl_setopt($ch, CURLOPT_URL, $url);
                curl_setopt($ch, CURLOPT_TIMEOUT, '60'); // in seconds
                curl_setopt($ch, CURLOPT_HEADER, 1);
                curl_setopt($ch, CURLOPT_NOBODY, 1);
                curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
                curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
                $res = curl_exec($ch);

                if(curl_getinfo($ch)['url'] == $url){
                    echo "not redirect";
                }else {
                    echo "redirect";
                }

Answer 5

I modified Adam Backstrom answer and implemented chiborg suggestion. (Download only HEAD). It have one thing more: It will check if redirection is in a page of the same server or is out. Example: terra.com.br redirects to terra.com.br/portal. PHP will considerate it like redirect, and it is correct. But i only wanted to list that url that redirect to another URL. My English is not good, so, if someone found something really difficult to understand and can edit this, you're welcome.

function RedirectURL() {
    $urls = array('http://www.terra.com.br/','http://www.areiaebrita.com.br/');

    foreach ($urls as $url) {
        $ch = curl_init();

        curl_setopt($ch, CURLOPT_HEADER, true);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        // chiborg suggestion
        curl_setopt($ch, CURLOPT_NOBODY, true);

        // ================================
        //  READ URL
        // ================================

        curl_setopt($ch, CURLOPT_URL, $url);
        $out = curl_exec($ch);

        // line endings is the wonkiest piece of this whole thing
        $out = str_replace("\r", "", $out);
        echo $out;

        $headers = explode("\n", $out);

        foreach($headers as $header) {
            if(substr(strtolower($header), 0, 9) == "location:") {
                // read URL to check if redirect to somepage on the server or another one.
                // terra.com.br redirect to terra.com.br/portal. it is valid.
                // but areiaebrita.com.br redirect to bwnet.com.br, and this is invalid.
                // what we want is to check if the address continues being terra.com.br or changes. if changes, prints on page.

                // if contains http, we will check if changes url or not.
                // some servers, to redirect to a folder available on it, redirect only citting the folder. Example: net11.com.br redirect only to /heiden

                // only execute if have http on location
                if ( strpos(strtolower($header), "http") !== false) {
                    $address = explode("/", $header);

                    print_r($address);
                    // $address['0'] = http
                    // $address['1'] = 
                    // $address['2'] = www.terra.com.br
                    // $address['3'] = portal 

                    echo "url (address from array) = " . $url . "<br>";
                    echo "address[2] = " . $address['2'] . "<br><br>";

                    // url: terra.com.br
                    // address['2'] = www.terra.com.br

                    // check if string terra.com.br is still available in www.terra.com.br. It indicates that server did not redirect to some page away from here.
                    if(strpos(strtolower($address['2']), strtolower($url)) !== false) {
                        echo "URL NOT REDIRECT";
                    } else {
                        // not the same. (areiaebrita)
                        echo "SORRY, URL REDIRECT WAS FOUND: " . $url;  
                    }
                }
            }
        }
    }
}