Resolve issues reported by PHPStan level 3

[AJenbo]

Type: refactoring

Level 3:

• return types
• types assigned to properties

[codecov]

Codecov Report

Attention: Patch coverage is 96.09375% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 92.70%. Comparing base (d595cd6) to head (0634353).

❗ Current head 0634353 differs from pull request most recent head cd525ac. Consider uploading reports for the commit cd525ac to get more accurate results

Files	Patch %	Lines
src/main/php/PHPMD/Parser.php	75.00%	1 Missing ⚠️
...HPMD/Rule/Controversial/CamelCaseParameterName.php	50.00%	1 Missing ⚠️
...PHPMD/Rule/Controversial/CamelCasePropertyName.php	50.00%	1 Missing ⚠️
...c/main/php/PHPMD/Rule/Design/LongParameterList.php	50.00%	1 Missing ⚠️
...ule/Naming/ConstructorWithNameAsEnclosingClass.php	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                3.x    #1101      +/-   ##
============================================
- Coverage     92.83%   92.70%   -0.14%     
- Complexity     1287     1289       +2     
============================================
  Files           111      114       +3     
  Lines          3418     3425       +7     
============================================
+ Hits           3173     3175       +2     
- Misses          245      250       +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.