How can I get product's pid URL? when I in the redirected URL?

[malin]

Every product has a pid link, but when I access it, it redirect to a new URL

 

 

You see my requests below:

[![enter image description here][1]][1]

[![enter image description here][2]][2]

  [1]: https://i.stack.imgur.com/pCD9y.jpg
  [2]: https://i.stack.imgur.com/Q2phV.jpg

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There have two HTTP requests, in my browser I request the first URL, you can see there is `bw=20M` param I added in the URI. 

but in the website it redirect to the second URL(`cart.php?a=confproduct&i=4`). 

now, in the page `cart.php?a=confproduct&i=4`, how can I get the URL which redirect to current URL?(I mean find the `car.php?a=add&pid=8&carttpl=McSpace&bw=20M`) , I want to get the `bw=20M` param.

 

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**EIDT-01**

In the cart.php?a=confproduct&i=4 link when I get document.referrer, it shows http://102.24.5.7/dedicated_servers, can not the URL cart.php?a=add&pid=8&carttpl=McSpace&bw=20M.