ini kenapa ya eror terus

PHP Fatal error:  Uncaught Error: Call to undefined function config() in /home/khayang2/public_html/app/core/data.php:3
Stack trace:
#0 /home/khayang2/public_html/app/config/autoload.php(8): require_once()
#1 /home/khayang2/public_html/app/server.php(16): require('/home/khayang2/...')
#2 /home/khayang2/public_html/index.php(17): require_once('/home/khayang2/...')
#3 {main}
  thrown in /home/khayang2/public_html/app/core/data.php on line 3