Improve this PHP bitfield class for settings/permissions?

I have been trying to figure out the best way to use bitmask or bitfields in PHP for a long time now for different areas of my application for different user settings and permissions. The farthest I have come so far is from a class contributed by svens in the Stack Overflow
post Bitmask in PHP for settings?. I have slightly modified it below, changing it to use class constants instead of DEFINE and making sure the get method is passed an int only. I also have some sample code to test the class’s functionality below.