Fix deprecations & Bump PHPStan level

[Z3d0X]

• Replaces the deprecated methods.
• adds dev dependency phpstan/phpstan-deprecation-rules - deprecated code detection for phpstan

[danharrin]

Hey @Z3d0X ! Sorry for not seeing this sooner. How much of this is still relevant?

[Z3d0X]

@danharrin Updated! phpstan (w/ phpstan/phpstan-deprecation-rules plugin) passes at current configured level of 5.

If you want i bump phpstan to a higher level

[danharrin]

if you want to work on fixing it for a higher level, go for it! but if not, dont worry about it

[Z3d0X]

@danharrin all done

[danharrin]

Thank you so much!