If the include path happens to be wrong (you can see your include path in the output of test.php, see Section 3.9.1), you could try the following:
Suppose your nuke files are in /usr/local/httpd/htdocs/nuke/html (just an example ). Suppose that this is the directory that contains
the includes directory beneath it. Then create a .htaccess file (Section 25.4) that contains the line
php_value include_path .:/usr/local/httpd/htdocs/nuke/html/includes
(no equal signs, just copy it in the .htaccess file). In most cases the include path will be correctly configured. In the few ones that it's not, the most probable cause of errors will be a
missing "current directory" (a missing dot in the include path).
If you have access to the php.ini file, you can do the same there. Find the line where include_path is defined and add the dot in the list, e.g.:
include_path = ".:/usr/local/httpd/htdocs/nuke/html/includes"
See also Warning: main(/db/db.php): failed to open stream and Fatal error: Failed opening required 'includes/sql_layer.php".