Fatal error: Uncaught Error: Undefined constant SampleCode\Constants::SUBSCRIPTION_INTERVAL_DAYS in /home/realtyevo/public_html/paymentApi/RecurringBilling/create-subscription-from-customer-profile.php:69 Stack trace: #0 {main} thrown in /home/realtyevo/public_html/paymentApi/RecurringBilling/create-subscription-from-customer-profile.php on line 69