I'm not sure if this is PHP or a Drupal thing, so bear with me. I'm very new to PHP and Drupal and have noticed that a lot of the functions I'm using, while creating a theme for it, that I've found around the internet tend to start like this:

function NAME($variables) {

or

function NAME($vars) {

or

function NAME(&$vars) {

I'd like to understand what this does. I get that what's inside the brackets is a parameter that gets passed to the function due to knowing some Javascript. But I don't understand where 'variables' comes from, exactly? And is $vars exactly the same thing as $variables, just a shortening? And in the third example, why the & before $vars?

 

Hope this question makes sense.

Ah, right - thank you.