How can I find where I will be redirected using cURL in PHP?

Question

I'm trying to make curl follow a redirect but I can't quite get it to work right. I have a string that I want to send as a GET param to a server and get the resulting URL.

Example:

String = Kobold Vermin
Url = www.wowhead.com/search?q=Kobold+Worker

If you go to that url it will redirect you to "www.wowhead.com/npc=257". I want curl to return this URL to my PHP code so that i can extract the "npc=257" and use it.

Current code:

function npcID($name) {
    $urltopost = "http://www.wowhead.com/search?q=" . $name;
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1");
    curl_setopt($ch, CURLOPT_URL, $urltopost);
    curl_setopt($ch, CURLOPT_REFERER, "http://www.wowhead.com");
    curl_setopt($ch, CURLOPT_HTTPHEADER, Array("Content-Type:application/x-www-form-urlencoded"));
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);
    return curl_getinfo($ch, CURLINFO_EFFECTIVE_URL);
}

This however returns www.wowhead.com/search?q=Kobold+Worker and not www.wowhead.com/npc=257.

I suspect PHP is returning before the external redirect happens. How can I fix this?

Answer 1

The answer above didn't work for me on one of my servers, something to to with basedir, so I re-hashed it a little. The code below works on all my servers.

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, false);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
$a = curl_exec($ch);
curl_close( $ch ); 
// the returned headers
$headers = explode("\n",$a);
// if there is no redirection this will be the final url
$redir = $url;
// loop through the headers and check for a Location: str
$j = count($headers);
for($i = 0; $i < $j; $i++){
// if we find the Location header strip it and fill the redir var       
if(strpos($headers[$i],"Location:") !== false){
        $redir = trim(str_replace("Location:","",$headers[$i]));
        break;
    }
}
// do whatever you want with the result
echo $redir;

Answer 2

Add this line to curl inizialization

curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);

and use getinfo before curl_close

$redirectURL = curl_getinfo($ch,CURLINFO_EFFECTIVE_URL );

es:

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt($ch, CURLOPT_USERAGENT,'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.13) Gecko/20080311 Firefox/2.0.0.13');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_BINARYTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT ,0); 
curl_setopt($ch, CURLOPT_TIMEOUT, 60);
$html = curl_exec($ch);
$redirectURL = curl_getinfo($ch,CURLINFO_EFFECTIVE_URL );
curl_close($ch);

Answer 3

Lot's of regex here, despite the fact i really like them this way might be more stable to me:

$resultCurl=curl_exec($curl); //get curl result
//Optional line if you want to store the http status code
$headerHttpCode=curl_getinfo($curl,CURLINFO_HTTP_CODE);

//let's use dom and xpath
$dom = new \DOMDocument();
libxml_use_internal_errors(true);
$dom->loadHTML($resultCurl, LIBXML_HTML_NODEFDTD);
libxml_use_internal_errors(false);
$xpath = new \DOMXPath($dom);
$head=$xpath->query("/html/body/p/a/@href");

$newUrl=$head[0]->nodeValue;

The location part is a link in the HTML sent by apache. So Xpath is perfect to recover it.

Answer 4

To make cURL follow a redirect, use:

curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);

Erm... I don't think you're actually executing the curl... Try:

curl_exec($ch);

...after setting the options, and before the curl_getinfo() call.

EDIT: If you just want to find out where a page redirects to, I'd use the advice here, and just use Curl to grab the headers and extract the Location: header from them:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, false);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($ch);
if (preg_match('~Location: (.*)~i', $result, $match)) {
   $location = trim($match[1]);
}

Answer 5

You can use:

$redirectURL = curl_getinfo($ch,CURLINFO_REDIRECT_URL);

Answer 6

Sometimes you need to get HTTP headers but at the same time you don't want return those headers.**

This skeleton takes care of cookies and HTTP redirects using recursion. The main idea here is to avoid return HTTP headers to the client code.

You can build a very strong curl class over it. Add POST functionality, etc.

<?php

class curl {

  static private $cookie_file            = '';
  static private $user_agent             = '';  
  static private $max_redirects          = 10;  
  static private $followlocation_allowed = true;

  function __construct()
  {
    // set a file to store cookies
    self::$cookie_file = 'cookies.txt';

    // set some general User Agent
    self::$user_agent = 'Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)';

    if ( ! file_exists(self::$cookie_file) || ! is_writable(self::$cookie_file))
    {
      throw new Exception('Cookie file missing or not writable.');
    }

    // check for PHP settings that unfits
    // correct functioning of CURLOPT_FOLLOWLOCATION 
    if (ini_get('open_basedir') != '' || ini_get('safe_mode') == 'On')
    {
      self::$followlocation_allowed = false;
    }    
  }

  /**
   * Main method for GET requests
   * @param  string $url URI to get
   * @return string      request's body
   */
  static public function get($url)
  {
    $process = curl_init($url);    

    self::_set_basic_options($process);

    // this function is in charge of output request's body
    // so DO NOT include HTTP headers
    curl_setopt($process, CURLOPT_HEADER, 0);

    if (self::$followlocation_allowed)
    {
      // if PHP settings allow it use AUTOMATIC REDIRECTION
      curl_setopt($process, CURLOPT_FOLLOWLOCATION, true);
      curl_setopt($process, CURLOPT_MAXREDIRS, self::$max_redirects); 
    }
    else
    {
      curl_setopt($process, CURLOPT_FOLLOWLOCATION, false);
    }

    $return = curl_exec($process);

    if ($return === false)
    {
      throw new Exception('Curl error: ' . curl_error($process));
    }

    // test for redirection HTTP codes
    $code = curl_getinfo($process, CURLINFO_HTTP_CODE);
    if ($code == 301 || $code == 302)
    {
      curl_close($process);

      try
      {
        // go to extract new Location URI
        $location = self::_parse_redirection_header($url);
      }
      catch (Exception $e)
      {
        throw $e;
      }

      // IMPORTANT return 
      return self::get($location);
    }

    curl_close($process);

    return $return;
  }

  static function _set_basic_options($process)
  {

    curl_setopt($process, CURLOPT_USERAGENT, self::$user_agent);
    curl_setopt($process, CURLOPT_COOKIEFILE, self::$cookie_file);
    curl_setopt($process, CURLOPT_COOKIEJAR, self::$cookie_file);
    curl_setopt($process, CURLOPT_RETURNTRANSFER, 1);
    // curl_setopt($process, CURLOPT_VERBOSE, 1);
    // curl_setopt($process, CURLOPT_SSL_VERIFYHOST, false);
    // curl_setopt($process, CURLOPT_SSL_VERIFYPEER, false);
  }

  static function _parse_redirection_header($url)
  {
    $process = curl_init($url);    

    self::_set_basic_options($process);

    // NOW we need to parse HTTP headers
    curl_setopt($process, CURLOPT_HEADER, 1);

    $return = curl_exec($process);

    if ($return === false)
    {
      throw new Exception('Curl error: ' . curl_error($process));
    }

    curl_close($process);

    if ( ! preg_match('#Location: (.*)#', $return, $location))
    {
      throw new Exception('No Location found');
    }

    if (self::$max_redirects-- <= 0)
    {
      throw new Exception('Max redirections reached trying to get: ' . $url);
    }

    return trim($location[1]);
  }

}

Answer 7

The chosen answer here is decent but its case sensitive, doesn't protect against relative location: headers (which some sites do) or pages that might actually have the phrase Location: in their content... (which zillow currently does).

A bit sloppy, but a couple quick edits to make this a bit smarter are:

function getOriginalURL($url) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_HEADER, true);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, false);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
    $result = curl_exec($ch);
    $httpStatus = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);

    // if it's not a redirection (3XX), move along
    if ($httpStatus < 300 || $httpStatus >= 400)
        return $url;

    // look for a location: header to find the target URL
    if(preg_match('/location: (.*)/i', $result, $r)) {
        $location = trim($r[1]);

        // if the location is a relative URL, attempt to make it absolute
        if (preg_match('/^\/(.*)/', $location)) {
            $urlParts = parse_url($url);
            if ($urlParts['scheme'])
                $baseURL = $urlParts['scheme'].'://';

            if ($urlParts['host'])
                $baseURL .= $urlParts['host'];

            if ($urlParts['port'])
                $baseURL .= ':'.$urlParts['port'];

            return $baseURL.$location;
        }

        return $location;
    }
    return $url;
}

Note that this still only goes 1 redirection deep. To go deeper, you actually need to get the content and follow the redirects.