Cannot access HTTP_POST_VARS without explicitly stating

I am having an issue with my server. I'm relatively new to PHP, so I've been looking over a lot of tutorials and articles lately. One common theme (and the reason I'm using PHP) is forms. The code typically uses an echo to pull the variabl from the HTTP_POST_VARS without explicitly stating it. IE, the tutorials use $name instad of $HTTP_POST_VARS["name"]. My problem is this, if I use $HTTP_POST_VARS["name"], it works just fine. If I just try to use $name, it shows up empty. The rest of the code will work fine. Any thoughts?