Warning: Undefined variable $countriesVisiting in /usr/www/users/realamxeyh/tour.php on line 23

Fatal error: Uncaught TypeError: in_array(): Argument #2 ($haystack) must be of type array, null given in /usr/www/users/realamxeyh/tour.php:23
Stack trace:
#0 /usr/www/users/realamxeyh/tour.php(23): in_array('15', NULL)
#1 {main}
  thrown in /usr/www/users/realamxeyh/tour.php on line 23