Magento Checkout is broken after SUPEE-11085 with PHP<5.5

Magento checkout page is broken after installing SUPEE-11085 (Authorize.net Direct Post Signature Key patch). Proceed to Checkout button results in a blank page, PHP fatal error is thrown: Fatal error: Can’t use method return value in write context in app/code/core/Mage/Authorizenet/Model/Directpost.php on line 392 Cause empty() function used in the patch with a function return value. As per official PHP documentation:Prior to PHP 5.5, empty() function only supports variables; anything else will result in a parse… Read the rest