Fatal error: Uncaught Error: Call to undefined function is_admin() in /users/nandini/www/wordpress-seo/admin/license-manager/samples/sample-plugin.php:22 Stack trace: #0 /users/nandini/www/wordpress-seo/admin/license-manager/samples/sample-plugin.php(74): Sample_Plugin->__construct() #1 {main} thrown in /users/nandini/www/wordpress-seo/admin/license-manager/samples/sample-plugin.php on line 22