oshrirozmarin we will need more details.
Are you writing code inside config.php
or are you trying to get values defined in config.php
from another part of the code ? Flarum has an url generator which is maybe what you ned ?
Unless you added your own blade templates via your extension there's normally no blade files to edit. You shouldn't alter anything in vendor
folder as it can be reverted by Composer anytime. To add content to head/footer there's a Document php extender.
If you can describe what you're trying to do in more details we can find links to other extensions you can take a look at to see how it was done.