从双重缩短的URL获取最终URL（t.co - > bit.ly - > final）

I couldn't convert a double shortened URL to expanded URL successfully using the below function I got from here:

function doShortURLDecode($url) {
        $ch = @curl_init($url);
        @curl_setopt($ch, CURLOPT_HEADER, TRUE);
        @curl_setopt($ch, CURLOPT_NOBODY, TRUE);
        @curl_setopt($ch, CURLOPT_FOLLOWLOCATION, FALSE);
        @curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
        $response = @curl_exec($ch);
        preg_match('/Location: (.*)
/', $response, $a);
        if (!isset($a[1])) return $url;
        return $a[1];
    }

I got into trouble when the expanded URL I got was again a shortened URL, which has its expanded URL.

How do I get final expanded URL after it has run through both URL shortening services?

Finally found a way to get the final url of a double shortened url. The best way is to use longurl api for it.

I am not sure if it is the correct way, but i am at last getting the output as the final url needed :)

Here's what i did:

<?php
 function TextAfterTag($input, $tag)
 {
        $result = '';
        $tagPos = strpos($input, $tag);

        if (!($tagPos === false))
        {
                $length = strlen($input);
                $substrLength = $length - $tagPos + 1;
                $result = substr($input, $tagPos + 1, $substrLength); 
        }

        return trim($result);
 }

 function expandUrlLongApi($url)
 {
        $format = 'json';
        $api_query = "http://api.longurl.org/v2/expand?" .
                    "url={$url}&response-code=1&format={$format}";
        $ch = curl_init();
        curl_setopt ($ch, CURLOPT_URL, $api_query );
        curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, 0);
        curl_setopt($ch, CURLOPT_HEADER, false);
        $fileContents = curl_exec($ch);
        curl_close($ch);
        $s1=str_replace("{"," ","$fileContents");
        $s2=str_replace("}"," ","$s1");
        $s2=trim($s2);
        $s3=array();
        $s3=explode(",",$s2);
        $s4=TextAfterTag($s3[0],(':'));
        $s4=stripslashes($s4);
        return $s4;
 }
 echo expandUrlLongApi('http://t.co/dd4b3kOz');
?>

The output i get is:

"http://changeordie.therepublik.net/?p=371#proliferation"

The above code works.

The code that @cryptic shared is also correct ,but i could not get the result on my server (maybe because of some configuration issue).

If anyone thinks that it could be done by some other way, please feel free to share it.

Perhaps you should just use CURLOPT_FOLLOWLOCATION = true and then determine the final URL you were directed to.

Since t.co uses HTML redirection through the use of JavaScript and/or a <meta> redirect we need to grab it's contents first. Then extract the bit.ly URL from it to perform a HTTP header request to get the final location. This method does not rely on cURL to be enabled on server and uses all native PHP5 functions:

Tested and working!

function large_url($url) 
{
    $data = file_get_contents($url); // t.co uses HTML redirection
    $url = strtok(strstr($data, 'http://bit.ly/'), '"'); // grab bit.ly URL

    stream_context_set_default(array('http' => array('method' => 'HEAD')));
    $headers = get_headers($url, 1); // get HTTP headers

    return (isset($headers['Location'])) // check if Location header set
        ? $headers['Location'] // return Location header value
        : $url; // return bit.ly URL instead
}

// DEMO
$url = 'http://t.co/dd4b3kOz';
echo large_url($url);

In case the problem is not a Javascript redirect as in t.co or a <META http-equiv="refresh"..., this is reslolving stackexchange URLs like https://stackoverflow.com/q/62317 fine:

public function doShortURLDecode($url) {
    $ch = @curl_init($url);
    @curl_setopt($ch, CURLOPT_HEADER, TRUE);
    @curl_setopt($ch, CURLOPT_NOBODY, TRUE);
    @curl_setopt($ch, CURLOPT_FOLLOWLOCATION, FALSE);
    @curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
    $response = @curl_exec($ch);
    $cleanresponse= preg_replace('/[^A-Za-z0-9\- _,.:
\/]/', '', $response);
    preg_match('/Location: (.*)[
]/', $cleanresponse, $a);
    if (!isset($a[1])) return $url;
    return parse_url($url, PHP_URL_SCHEME).'://'.parse_url($url, PHP_URL_HOST).$a[1];
}

It cleans the response of any special characters, that can occur in the curl output before cuttoing out the result URL (I ran into this problem on a php7.3 server)