This program simply does one thing.
It creates a function is_class to go along with the many other 'is' functions.
is_object exists although it will return true if you execute is_object(new \stdClass()) to me that seems like unexpected behavior. When somebody wants to find out if something is a class, they are usually not testing \stdClass.
is_a exists, but you need to know the name of the class in question. You simply can't call is_a($class);.
This function can be called as is_class($class), which will return true for interfaces or traits.
The second way is is_class($class, true), where true means strict, which will return false if anything is an interface or trait.
The function always returns false for \stdClass, you can use is_object for that, unless you extend \stdClass.
phpunit