Grab the page which is redirecting

I am trying to grab a file .pdf from a server. There is a hyperlink at the page, by clicking that link it goes to a page, it checks for some privileges, then it redirects to anoth开发者_StackOverflower page which shows the content of the .pdf within an Iframe.

lets say beginning url is http://site.com/docs/1.pdf on click it goes to another page, then another one and it comes whth the last page http://site.com/viewer/pdfs/1.pdf the last page shows the pdf content within an Iframe.

I realized that the software IDM (Internet download manager) can follow the redirections and download the file by clicking the first link.

I was wondering if there is an algorithm or library or class or hint that I can figure out how to do that in PHP scripting.

by the way, once I wrote a code to read the header of the page and I could redirect to the second page, but I want to know if there is a general algorithm for this or not.

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If you are doing the HTTP stuff manually, check for 30x statuscodes and the Location header.

However, you could simply use CURL and set CURLOPT_FOLLOWLOCATION.

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Yes, just like ThiefMaster said, you could look for the Location header. Have a look here, maybe this can be a help to you: http://codesnippets.joyent.com/posts/show/1214 This function retrieves file size of a remote file, why don't you try to change it slightly so that it gets the final URL?