Fatal error: Uncaught Error: Call to undefined function add_action() in C:\xampp\htdocs\wp-content\plugins\advanced-custom-fields\includes\forms\form-attachment.php:31 Stack trace: #0 C:\xampp\htdocs\wp-content\plugins\advanced-custom-fields\includes\forms\form-attachment.php(214): acf_form_attachment->__construct() #1 {main} thrown in C:\xampp\htdocs\wp-content\plugins\advanced-custom-fields\includes\forms\form-attachment.php on line 31