I keep getting this error and IDK php can I replace the whole file somehow?
Fatal error: Uncaught Error: Call to undefined function get_template_directory() in /home/campbel/public_html/wp-includes/functions.php:8580 Stack trace: #0 /home/campbel/public_html/wp-settings.php(98): require() #1 /home/campbel/public_html/wp-config.php(91): require_once('/home/campbel/p...') #2 /home/campbel/public_html/wp-load.php(37): require_once('/home/campbel/p...') #3 /home/campbel/public_html/wp-blog-header.php(13): require_once('/home/campbel/p...') #4 /home/campbel/public_html/index.php(17): require('/home/campbel/p...') #5 {main} thrown in /home/campbel/public_html/wp-includes/functions.php on line 8580
The best course of action is to update or reinstall your WP. Don't forget to create a backup copy before you do anything (including the database).