Fatal error: Uncaught Braintree\Exception: The Braintree library requires the xmlwriter extension. in /var/www/html/Braintree_3DS_V2/braintree-php-4.2.0/lib/Braintree.php:18 Stack trace: #0 /var/www/html/Braintree_3DS_V2/braintree-php-4.2.0/lib/Braintree.php(24): Braintree::requireDependencies() #1 /var/www/html/Braintree_3DS_V2/getClientToken.php(28): require_once('...') #2 /var/www/html/Braintree_3DS_V2/Braintree3DSv2.php(3): require_once('...') #3 {main} thrown in /var/www/html/Braintree_3DS_V2/braintree-php-4.2.0/lib/Braintree.php on line 18