Fatal error: Uncaught Error: Class 'WP_Upgrader' not found in /home2/cp299447/public_html/watthumpla.ac.th/wp-admin/includes/class-core-upgrader.php:25
Stack trace:
#0 {main}
thrown in /home2/cp299447/public_html/watthumpla.ac.th/wp-admin/includes/class-core-upgrader.php on line 25