PHP—“Defined or Exit” at the beginning of many files?

Question

I have been inspecting some PHP source codes and I more often than not find files starting with

defined(\'__someconstant__\') or exit();

I

Answer 1

Isn't there (even non-PHP based) a cleaner way of doing it without introducing this extra code in every file?

Presence of such snippets indicate bad code structuring, namely code automatically executing in global scope. You shouldn't have this or exit(); code in pure function/class includes. It would be redundant there.

Code that does perform potentially dangerous actions shoult not be web-accessible in the first place. The or exit; approach is a workaround. It should always be accompanied by a FilesMatch and Deny from All in a .htaccess file however. Best set the whole include directory inaccessible.