PayPal 1.7.0: major stabilization work for modern Geeklog sites

A substantial modernization effort has been completed on the Geeklog PayPal plugin in preparation for version 1.7.0.

This release focuses on making the existing plugin safer and more reliable on current environments while preserving compatibility with older Geeklog installations.

The target range is now Geeklog 2.1.1 through 2.2.2 and PHP 5.6 through PHP 8.x.

Among the most important changes are improved PHP 8 compatibility, safer install/upgrade/uninstall handling, a reorganized configuration interface with contextual help, modernized administration pages, improved cart persistence, cleaner checkout pages, dynamic Geeklog blocks, and better handling of PayPal Sandbox and merchant settings.

The cart and checkout experience has also received significant attention. Empty cart blocks are handled correctly, the checkout process is clearer and more responsive, shipping and payment methods are easier to understand, and buyers are better informed that card payment may be available through PayPal without requiring a PayPal account.

The historical PayPal autotags are preserved, and the new [paypal:count] autotag implements the long-standing request to display the current number of items in the visitor's cart.

This work also addresses existing issues from the PayPal repository, including the PHP compatibility problem reported in issue #3 and the cart-count autotag requested in issue #1.

PayPal 1.7.0 deliberately keeps the existing Website Payments Standard, IPN and NVP/SOAP payment architecture so existing sites can upgrade without a disruptive payment migration. A future major version can then focus on the current PayPal Checkout and REST APIs.

The plugin is available from the official Geeklog Plugins repository:

https://github.com/Geeklog-Plugins/paypal

The objective of this release is simple: provide Geeklog administrators with a stable and modernized PayPal plugin while preserving a safe upgrade path for existing installations.