Drupal7: show 404 page after checks in preprocessing

Question

I have some checks in my preprocessing files for nodes. If one of them is true I would like to show my defined 404 page. How is this possible with a php call?

Answer 1

Use this code:

if([YOUR_CHECKS]){
    drupal_not_found();
}

Answer 2

You should use the drupal_not_foun() function