How to pick domain name from an url string with php regex?

Hello,

I have a problem, I have several url strings like below:


http://www.mysite.com/?action=1234
http://www.mysite.com/doit.php?=abc
http://www.mysite.com/category/myarticle/
http://mysite.com/myresearch/15.html
http://subdomain.mysite.com/thelist/abcd.php
...
..
.


The list goes on and on, is there any regex func that fits all the endless posibilities to pick up the domain name "mysite.com" from the url strings?

Any help greatly appreciated...
Thx