If you upgrade to SubscriptionBoss 1.14 but have not performed the mandatory upgrade to PHP 5.3 or 5.4 then your buyers will encounter an error during the payment process for subscriptions with immediate payment after they the click the “Agree and Pay” on PayPal but before payment is actually taken. Any purchases involving products or subscriptions that have a “billing delay” are not affected.
The error that is displayed will depend on the configuration of PHP error reporting on your site. This can vary according to your server settings and the WordPress settings.
Some users will see the error:
Call to undefined function date_diff() in /home/?????/public_html/??????/wp-content/plugins/subscriptionboss/subb-functions.php on line 256
For others there will be a more general server error:
Whichever error is displayed the solution is to upgrade you server to a stable version of PHP, either 5.3.13 or 5.4.3 as found on the PHP download page
I am sorry for any inconvenience that this has caused.
In the next release of SubscriptionBoss I have included a PHP version checker so it will be explicit what version of PHP is a pre-requisite for each new release of SubscriptionBoss.