PHP - Advantages Of Closures

Hiya,

I'm still hesitant on starting my project, as I am unsure whether or not to code everything using classes or not. Whilst searching the net for inspiration, I came across this script on Code Canyon.

Does this script have to be coded in a class, or can the same results be achieved by simply using functions. What would be the main advantage(s) for coding such a script using classes?

This is still something I have difficulty getting my head around.
I would appreciate any body's thoughts on this topic.

Thanks,
FishSword

Trying to improve my script-architecture, I got curious about other ways to pass application-data around aside from using the$GLOBALS array. The only other way I really found was to use an object called a "Registry". I just ended up being confused regarding when which method is better than the other, let alone how to even use a registry-object in my scripts. So my questions a
- When is it better to use a registry object in place of global data?
- how would you use a registry?
- how would a registry object get passed around, through other objects and functions?

Heres the registry I found...
class registry {
var $_cache_stack = array();

function __construct(){
$this->_cache_stack = array(array());
}
function set($key, &$item){
$this->_cache_stack[0][$key] = &$item;
}
function &get($key){
return $this->_cache_stack[0][$key];
}
function isEntry($key){
return ($this->getEntry($key) !== null);
}
function &instance(){
static $registry = false;
if (!$registry) $registry = new Registry();
return $registry;
}
function save(){
array_unshift($this->_cache_stack, array());
if (!count($this->_cache_stack)) exit('Registry lost!');
}
function restore(){
array_shift($this->_cache_stack);
}
}