How can I display the PHP error instead of giving me 500 Internal Server Error?

To turn on PHP error reporting / show errors on a per file bases. You will need to wirting below code at the top of the PHP file.

<?php
error_reporting(E_ALL);
ini_set('display_errors', 'On');

Put this above code at the top of your .php file. Save the file. Then option the .php page link in the web browser, you will then see the actual error stopping to run you php code (if any).