PHP cURL: Get target of redirect, without following it

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The curl_getinfo function returns a lot of metadata about the result of an HTTP request. However, for some reason it doesn\'t include the bit of information I want at the m

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南笙

2021-01-02 10:54
I had the same problem and curl_setopt($ch, CURLOPT_FOLLOWLOCATION, false); was of any help.

So, I decided not to use CURL but file_get_contents instead:
```
$data = file_get_contents($url);
$data = str_replace("<meta http-equiv=\"Refresh\" content=\"0;","<meta",$data);
```
The last line helped me to block the redirection although the product is not a clean html code.

I parsed the data and could retrieve the redirection URL I wanted to get.
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Happy的楠姐

2021-01-02 11:07

No there is no more efficient way
Your can use CURLOPT_WRITEHEADER + VariableStream
So.. you could write headers to variable and parse it

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小鲜肉

2021-01-02 11:10
You can simply use it: (CURLINFO_REDIRECT_URL)
```
$info = curl_getinfo($ch, CURLINFO_REDIRECT_URL);
echo $info; // the redirect URL without following it
```
as you mentioned, disable the CURLOPT_FOLLOWLOCATION option (before executing) and place my code after executing.

CURLINFO_REDIRECT_URL - With the CURLOPT_FOLLOWLOCATION option disabled: redirect URL found in the last transaction, that should be requested manually next. With the CURLOPT_FOLLOWLOCATION option enabled: this is empty. The redirect URL in this case is available in CURLINFO_EFFECTIVE_URL

Refrence
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南方客

2021-01-02 11:11

This can be done in 4 easy steps:

Step 1. Initialise curl

curl_init($ch); //initialise the curl handle
//COOKIESESSION is optional, use if you want to keep cookies in memory
curl_setopt($this->ch, CURLOPT_COOKIESESSION, true);

Step 2. Get the headers for $url

curl_setopt($ch, CURLOPT_URL, $url); //specify your URL
curl_setopt($ch, CURLOPT_HEADER, true); //include headers in http data
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, false); //don't follow redirects
$http_data = curl_exec($ch); //hit the $url
$curl_info = curl_getinfo($ch);
$headers = substr($http_data, 0, $curl_info['header_size']); //split out header

Step 3. Check if you have the correct response code

if (!($curl_info['http_code']>299 && $curl_info['http_code']<309)) {
  //return, echo, die, whatever you like
  return 'Error - http code'.curl_info['http_code'].' received.';
}

Step 4. Parse the headers to get the new URL

preg_match("!\r\n(?:Location|URI): *(.*?) *\r\n!", $headers, $matches);
$url = $matches[1];

Once you have the new URL you can then repeat steps 2-4 as often as you like.

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傲寒

2021-01-02 11:12

curl doesn't seem to have a function or option to get the redirect target, it can be extracted using various techniques:

From the response:

Apache can respond with a HTML page in case of a 301 redirect (Doesn't seem to be the case with 302's).

If the response has a format similar to:

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>301 Moved Permanently</title>
</head><body>
<h1>Moved Permanently</h1>
<p>The document has moved <a href="http://www.xxx.yyy/zzz">here</a>.</p>
<hr>
<address>Apache/2.2.16 (Debian) Server at www.xxx.yyy Port 80</address>
</body></html>

You can extract the redirect URL using DOMXPath:

$i = 0;
foreach($urls as $url) {
    if(substr($url,0,4) == "http") {
        $c = curl_init($url);
        curl_setopt($c, CURLOPT_RETURNTRANSFER, true);
        $result = @curl_exec($c);
        $status = curl_getinfo($c,CURLINFO_HTTP_CODE);
        curl_close($c);
        $results[$i]['code'] = $status;
        $results[$i]['url'] = $url;

        if($status === 301) {
            $xml = new DOMDocument();
            $xml->loadHTML($result);
            $xpath = new DOMXPath($xml);
            $href = $xpath->query("//*[@href]")->item(0);
            $results[$i]['target'] = $href->attributes->getNamedItem('href')->nodeValue;
        }
        $i++;
    }
}

Using CURLOPT_NOBODY

There is a faster way however, as @gAMBOOKa points out; Using CURLOPT_NOBODY. This approach just sends a HEAD request instead of GET (not downloading the actual content, so it should be faster and more efficient) and stores the response header.

Using a regex the target URL can be extracted from the header:

foreach($urls as $url) {
    if(substr($url,0,4) == "http") {
        $c = curl_init($url);
        curl_setopt($c, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($c, CURLOPT_NOBODY,true);
        curl_setopt($c, CURLOPT_HEADER, true);
        $result = @curl_exec($c);
        $status = curl_getinfo($c,CURLINFO_HTTP_CODE);
        curl_close($c);
        $results[$i]['code'] = $status;
        $results[$i]['url'] = $url;

        if($status === 301 || $status === 302) {
            preg_match("@https?://([-\w\.]+)+(:\d+)?(/([\w/_\-\.]*(\?\S+)?)?)?@",$result,$m);
            $results[$i]['target'] = $m[0];
        }
        $i++;
    }
}

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