In PHP, they aren't known as "scopes", they are "super globals." Specific arrays which have a global scope, reguardless where you are in your script.
You can read all about them on PHP's site: http://us2.php.net/manual/en/language.variables.predefined.php
_REQUEST is a combination of _GET, _POST and _COOKIE. It's really an ugly beast and should only be used if you expect if you really don't know which array your variable is coming from.
On top of all that, based on your posted code, be very, very careful when using the arrays directly. Remember, just because your form requires "name" it does not mean that your _POST key value will be "name." If you get what I'm saying.
OO vs procedural programming. ha
Personally, I prefer the OO method. It's actually extremely simple once you understand it. My background was in C++ programming, so when PHP came OO, I leapt on it! PHP's OO design is very much like Java's, which is another language I learned just before I moved to PHP5, which made things so much easier. Play around with it, you'll understand it. OO, at it's core, is extremely simple.
yerba# rm -rf /etc