Cacher is the code snippet organizer for pro developers

https://www.simonholywell.com/post/2013/04/three-things-i-set-on-new-servers/
https://engineeredweb.com/blog/2013/secure-site-clickjacking-x-frame-options/

http://www.kobashicomputing.com/prevent-clickjacking-of-your-websites

1)  Apache
Header always append X-Frame-Options SAMEORIGIN

2) Nginx
add_header X-Frame-Options SAMEORIGIN;

3) htaccess
Header append X-FRAME-OPTIONS "SAMEORIGIN"

4) PHP:
header('X-Frame-Options: SAMEORIGIN');

5) Drupal:
  drupal_add_http_header('X-Frame-Options', 'SAMEORIGIN');