vBulletin URL replace code

I was previously asking for a smiliar function, but no o开发者_开发问答ne of them are like the vBulletin 4 has.

I mean if I paste some URL's in the vBulletins text box it will replace them for example like this:

Input:

http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior
http://yahoo.com/

Output:

php - How to mimic StackOverflow Auto-Link Behavior - Stack Overflow
Yahoo!

And this is the best of all, because if the URL doesn't exist (or don't have tags) it'll just stay with the URL path!

Input:

http://fake.url

Output:

http://fake.url

Then message BBCODE looks following:

[url=http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior]php - How to mimic StackOverflow Auto-Link Behavior - Stack Overflow[/url]
[url=http://yahoo.com/]Yahoo![/url]
[url]http://fake.url[/url]

How do they do that? Is it possible to do with PHP/JS? If so, could you direct me how?

Kind Regards,

Lucas.

---

You have to:

1. parse the input to extract the URLs(there should be many related topics on SO)
2. request the URL's to get the contents of the <title/>
3. Build the BBCode regarding to the response

This can be done using PHP, JS-only will not be able, because it may not parse external documents.(But of course you can setup a proxy-script on serverside that requests the document and returns the title to javascript/AJAX)