While the Object Calisthenics principles are:
- Use only one level of indentation per method
- Don’t use the else keyword
- Wrap all primitives and strings
- Use only one dot per line
- Don’t abbreviate
- Keep all entities small
- Don’t use any classes with more than two instance variables
- Use first-class collections
- Don’t use any getters/setters/properties
I am not sure why those rules should be considered calisthenic.
They should be considered a base foundation for coding. If you don’t do those, then you can’t even walk. They are not any kind of calisthenic.
Also, I am happy that the examples are in PHP which speaks that PHP is no more the swamp it was before.