[PHP] Getting information from sites

I was wondering if there was any way to get particular information from a web site. Such as the <meta> tag information or other links inside the page that have http://www.blah.com in them. I know how i open the site and read it and can store the hole site, but dont know how to get certain bits of it out of the source.

If this is confusing :frowning: let me know.

Thanks!