fix(phpstan): code improvements and resolve warnings

Reviewed code and made several improvements which provide better error handling, code quality, and resolved warnings. The changes include:

• Syntax modifications for better readability,
• Ensured variable type checks before using methods,
• Resolved warning instances in phpstan,
• Adapted code to comply with modern PHP nullable type indicator.

Alongside, made version update in phive/phars.xml. Also, unnecessary comments or instances are removed for a cleaner code.

Related: #16 (closed)

.gitlab-ci.yml

@@ -14,4 +14,4 @@ phpunit-php8.2:
 # Remove the entire phpunit-php8.3 block, to allow PHPUnit to run on PHP 8.3 in your pipeline
 phpunit-php8.3:
   rules:
-    - when: never
\ No newline at end of file
+    - when: never