Fatal error: Uncaught Error: Call to undefined function wp() in /var/www/html/wp-blog-header.php on line 16

Error: Call to undefined function wp() in /var/www/html/wp-blog-header.php on line 16

Call Stack:
    0.0003     355504   1. {main}() /var/www/html/index.php:0
    0.0004     355784   2. require('/var/www/html/wp-blog-header.php') /var/www/html/index.php:17