Trigger 500 Internal Server Error in PHP and display Apache error page

Question

How can i trigger 500 Internal Server Error or 404 Page Not Found Apache errors in PHP?

For 500 Internal Server Error i have tried

Answer 1

On PHP 5.5 => "header("tester.php",true,500);" where tester.php does not exist. It works and takes me to my 500 page :)

Unfortunately none of the other methods listed here worked for me for one reason or the other.