franz-josef-kaiser/WordPress-GitHub-Plugin-Updater — comment on commit c0699239965d2c5e850b89d9f8ad5ded7a755bdd
File: updater.php line 3
By GaryJones:

If it was necessary, it would be in WordPress core code, but there's not a single instance of it in any file. I've also never noticed in any plugin, or any theme code, even the popular ones, so if it was important, someone would have complained by now.

Also, the encoding directive wasn't supported until PHP 5.3, and even then only when it's compiled with `--enable-zend-multibyte`. In the meantime, anyone who is using 5.3.1 may well experience issues when requiring a file like this which has a `declare` at the top of it - https://bugs.php.net/bug.php?id=50464.

So, adding it in will only, at best, do absolutely nothing useful, and at worst, cause fatal errors.