Sometimes, you may encounter with a website showing 500 internal server error and in apache error logs, it shows the following error message.
SecurityException in Application.cpp:188: Do not have root privileges. Executable not set-uid root?
Premature end of script headers: index.php
This error is because of the suphp binary which is missing its sticky/suid permissions. It can be fixed by executing the following command.
# chmod +s /opt/suphp/sbin/suphp
Once permissions are corrected, check the website, it should be working fine now.