Resolve PHPStan-Strict errors: variable.undefined

Note: the changes in the MR are with polluteScopeWithLoopInitialAssignments turned off, as I believe including them right now would be an overall major style change. Instead, we may consider re-working the logic a bit.

E.g polluteScopeWithLoopInitialAssignments disallows re-cyling the assignment part of for ($i=0; $i<3; $i++) outside of the loop. The neatest way of abiding by this configuration, is by changing things to while AFAIK.

These are the remaining variable.undefined items that need to be fixed with polluteScopeWithLoopInitialAssignments =false per strict rules.