Parsing out “site.com” from a passed variable in PHP?

[nazmina]

I'm passing through a variety of URLs in a global variable called target_passthrough, so the URL of a page might look like:http://www.mysite.com/index.php?target_passthrough=example.comOr something like that. Formats for that variable may be a variety of things such as (minus quotes):[*]"www.example.com"[*]".example.com"[*]"example.com"[*]"http://www.example.com"[*]".example.com/subdir/"[*]".example.com/subdir/page.php"[*]"example.com/subdir/page.php"Please note how some of those have periods as the first character such as 2,5, and 6.Now, what I am trying to do is pull out just "example.com" from any of those possible scenarios with PHP and store it to a variable to echo out later. I tried parse_url but it gives me the "www" when that is present, which I do not want. In instances where the url is just "example.com" it returns a null value.I don't really know how to do regex matching or if that is even what I need so any guidance would be appreciated--not really that advanced at php.