URL checking

Hi, I'm very much a newbie! I'm trying to set up a site which will automatically test links in a large link directory and show date and time of last check and whether or not a link to the external URL was dead or alive at the time. On looking at the PHP manual it is not completely obvious which function I should be using, does fopen achieve this; how does it handle a site such as http://www.bloggs.com where the default file might be index.htm or default.php and what does it do if a 404 error is encountered, does it recognize that in fact no file has been found? I hope this makes sense and that someone can point me in the right direction :} Many thanks, TonyK