Getting domain name

[squimmy]

Is there a way i can do this

if (this site is http://www.aexampledomain.com){
do this
}else{
do that
}

I really need a function which returns the domain name the user is on. For instance it will check if you are on http://www.awgaeg.com instead of http://www.areukyawefkuyg.com

if not, is there a equivalent javascript function which a can also return the address of the site?

Thanks

[mtmosier]

if ($_SERVER['HTTP_HOST'] == 'www.example.com') {