Add integration/authentication for Yii1 framework running on php8 server.

[kenguest]

Some changes required to get kcfinder working with an integration for testing against Yii for authentication:

• Use extension_loaded instead of class_exists so Yii's autoloader isn't triggered.
• Similarly use extension_loaded instead of function_exists
• The 'each' keyword was removed in PHP 8.0 - alternative/fix added.