reformatted and updated source to use php7.4 typehinting, removed leg…

[silentgecko]

…acy deps, upgraded deps to newer versions

Proposed changes

Upgrade Project to PHP 7.4 and higher

Types of changes

• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• [x] I have read the CONTRIBUTING doc
• [x] Lint and unit tests pass locally with my changes
• [x] I have added/updated necessary documentation in the README.md or doc/ directories (if appropriate)

Further comments

i wanted to upgrade this project to php7.4, because we're currently updating all of our projects, and this is one of the dependencies. i mean, no update since a couple of years, this earned a little bit of refreshment ;)

I suggest to tag this as version 2.X, so people who want to use the older version are still able to Tip: i replaced all tabs with whitespaces, maybe you want to ignore whitespace changes