refactor: code improvements with php_codesniffer without affecting logic, part 1

[marcosmarcolin]

Hello,

don't be scared by so many changes, they don't change the operating logic at all, it's just code quality.

I'm interested in contributing more to the project, and would start by updating parts of the code to industry-accepted standards.

I'll separate it into 'small' parts to make it less difficult to review, if you accept it of course (:

I installed squizlabs/php_codesniffer initially.

To review the code, run vendor/bin/phpcs src, to automatically correct use: vendor/bin/phpcbf src.

Well, that's it, it went well.

[walkor]

Merged and thank you for your effort in improving the code quality. 👍