Upgrading Better Together for OpenCart

Better Together is a BOGO discounting module I created for Zen Cart.  I have ported the logic to a few other carts (osCommerce, Prestashop, and OpenCart), and this post pertains to the OpenCart port.

The first release of the Better Together for OpenCart module was for OpenCart 1.5.  Then I made a handful of tweaks for compatibility with version 2.0.  Now I knew I had to upgrade for 2.3 compatibility, but since the version 2 changes were pretty easy, I honestly thought upgrading for version of OpenCart would be trivial.  I was wrong!  There were a few tricky things, and I’ll share them here in case other software developers are working on upgrading their pre-2.3 extensions.

  1. The file paths are different.  All file paths now include “extension” directories.  So instead of catalog/model/total/better_together.php, the file path becomes catalog/model/extension/total/better_together.php.
  2. The inheritance hierarchy is different.  So instead of declaring your model class as ModelYourClass, it’s ModelExtensionYourClass, which extends Model.
  3. This is what really tripped me up.  Because the 2.3 base class overrides getters and setters, you have to be sure to declare all your class variables so that magic methods won’t be used to access them(*).  If you came out of PHP4, this is a bit of an adjustment, but there you are.  The positive thing is that it makes your code more self-documenting.

(*) If you don’t do this, you’ll get the “Indirect modification of overloaded property has no effect” fatal error.