Fatal error: Uncaught Error: Call to undefined function Cornerstone\TwigIntegration\add_filter() in /home/waterengineering/public_html/wp-content/plugins/cornerstone/includes/integration/Twig/src/TwigExtensions/WordPressExtension.php:11 Stack trace: #0 {main} thrown in /home/waterengineering/public_html/wp-content/plugins/cornerstone/includes/integration/Twig/src/TwigExtensions/WordPressExtension.php on line 11