You're probably just confusing the variable scope of the variables in question. First, does your php.ini have register_globals set to "on"? If it is NOT on, then the variables are only available in the appropriate registers: query string variables go in $GET[], and form-posted variables go in $POST[].
If your register_globals is on, then all the variables should be available as globals, but if you call from inside functions or included files, there's a good chance you may need to declare the variable global first. If you don't "see" the variable, try declaring it global first.
print "Foo is " . $foo . "<BR>"; // prints "Foo is "
global $foo;
print "Foo is " . $foo . "<BR>"; // prints "Foo is bar"
This sort of situation can happen if you have a global variable $foo that is equal to "bar", but the code above is contained within a function. The function has a local scope for any variable UNTIL you declare it global. So you cannot access a global without declaring it. Local variables are destroyed upon the end of the function call -- but if a function declares a variable global and modifies it, those changes remain after the end of the function. That's important to remember, too. That's the 'other' (and worse) way to getting a value out of a function, aside from returning it.
