empty() behaviour in Filter properties

[nohponex]

empty($filter->primary) is not working as expected, same applies for classes with magic properties

Solution:

https://stackoverflow.com/questions/2045791/php-empty-on-get-accessor

Based on a reading of the empty's manual page and comments (Ctrl-F for isset and/or double underscores), it looks like this is known behavior, and if you want your __set and __get methods and empty to play nice together, there's an implicit assumption that you implement a __isset magic method as well.