PHP $GLOBALS Suggestion

I noticed Interspire Shopping Cart initializes a lot of it's classes to a PHP's $GLOBAL开发者_如何学GoS variable. Is there any performance or security issues when doing this?

Below is a fake file but written similar to that of Interspire Shopping Cart's.

<?php 
// account.php

$GLOBALS['USER_ACCOUNT'] = new USER_ACCOUNT();
$GLOBALS['USER_ACCOUNT']->createPage(); //creating the page

?>

I have noticed that within the process of creating the page (see above) other files that get included will need access to the $GLOBALS['USER_ACCOUNT']. So this class instance will be needed by others later down the line.

Is there any performance or security issues when doing this?

No, but it is a bad practice. Storing data in the global scope can be a sign of bad design. Excessive globals are a "code smell," but I'm not getting that from this specific use.

As mentioned in the comments, they seem to be abusing globals instead of implementing the Registry pattern, which is designed to allow for exactly this type of behavior without contaminating the global scope.

Many other languages don't actually have a global scope for variables, meaning that they'd have to use Registry (or something like it) instead. PHP just happens to make it easy to do the wrong thing.

Using a Registry rather than globals also can make it easier to perform automated testing on the code.