PHP Script that checks if URL exists online
<p>I wanted to build a program in PHP my clients could use to check facebook, myspace and youtube url usernames, for the lack of better words.
I do believe Facebook calls these usernames(www.facebook.com/<strong>username</strong>).</p>

<p>I just need a form that a client could enter a value into, and then on the server side it would check to see if the "username" was taken, or in use by one of these sites above. If it wasn't in use, it would just echo out "Not in use.".</p>

<p>Where would I began to learn about what it would take to build this in PHP. Or is it easier then I am making it out to be?</p>
