Minor code improvements

[viktoras25]

Hello Barry and maintainers

thank you very much for the library. I would want to suggest a couple of minor changes to the code:

1. Shortened some FQNs, since they are already use'd anyway
2. Used constants for HTTP codes
3. An empty already checks warnings for an empty array, so count is superfluous. At the same time, it's not checked for being iterable before put into a foreach.

I hope you can find these useful. Feel free to decline if they are not in line with your guidelines.