refactor: code stability

Code stability -> missing return types, qualifier imports, code cleanup, function converts to php8.1

.phive/phars.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<phive xmlns="https://phar.io/phive">
+  <phar name="phpstan" version="^1.10.67" installed="1.10.67" location="./tools/phpstan" copy="false"/>
+</phive>