PHP global or $GLOBALS

Well, you should only use globals in limited circumstances, but to answer your question:

1. global is potentially marginally faster (it will rarely make a difference).
2. $GLOBALS (not $GLOBAL) is more readable, because every time you see it, you know you are accessing/changing a global variable. This can be crucial in avoiding nasty bugs.
3. Inside the function, if you want to unset a global variable, you must use unset($GLOBALS['varname']), not global $varname; unset($varname);.

As to points 1 and 2, I’ll quote Sara Golemon here:

What does that mean for your use of the $GLOBALS array? That’s right, the global keyword is technically faster. Now, I want to be really clear about one thing here. The minor speed affordance given by using your globals as localized [compiled variables] needs to be seriously weighed against the maintainability of looking at your code in five years and knowing that $foo came from the global scope. something_using($GLOBALS['foo']); will ALWAYS be clearer to you down the line than global $foo; /* buncha code */ something_using($foo); Don’t be penny-wise and pound foolish..