Question

I’m creating a basic framework in PHP. I need to pass data for the current page into different functions, allow them to modify and save it, and then pass it back to the page to be displayed. I was originally planning on storing the data in a global variable like $GLOBALS['data'], but I’m starting to think that using a global is a bad idea. So I’m thinking that instead I will put a static variable in the system class, and access it using system::$data. So, my question is, which would be better and why?

This:

$GLOBALS['data'] = array();
$GLOBALS['data']['page_title'] = 'Home';
echo $GLOBALS['data']['page_title'];

Or this:

class system
{
    public static $data = array()
}

function data($new_var)
{
    system::$data = array_merge(system::$data, $new_var);
}

data(array('page_title' => 'Home'));
echo system::$data['page_title'];

Answer 1

There really is no difference between a global variable and a public static variable. The class variable is namespaced a tiny bit better, but that hardly makes any difference. Both are accessible anywhere at any time and both are global state.

As it happens, I just wrote an exhaustive article on the subject:
How Not To Kill Your Testability Using Statics