I was doing some local PHP development using the built-in PHP web server, e.g.:

php -S localhost:5000

I had a failing statement, and all I was getting was an Internal Server Error message. I finally tracking down the problem by adding the following statements (temporarily) to my PHP code:

error_reporting(2047);
 
ini_set("display_errors",1);

This caused verbose logging to be dumped to my browser, allowing me to understand the problem.