Fatal error: Uncaught Error: Call to undefined function wp() in /volume1/wordpress/wordpress1/wp-blog-header.php on line 16

Error: Call to undefined function wp() in /volume1/wordpress/wordpress1/wp-blog-header.php on line 16

Call Stack:
    0.0001     361544   1. {main}() /volume1/wordpress/wordpress1/index.php:0
    0.0001     361856   2. require('/volume1/wordpress/wordpress1/wp-blog-header.php') /volume1/wordpress/wordpress1/index.php:17