What does the __FUNCTION__ constant return?

The FUNCTION constant is specifically designed to return the name of the current function where it is called. When this constant is used within a function, it provides a string that represents the function's name, making it very useful for debugging or logging purposes.

For instance, if you define a function named 'myFunction' and within this function you use echo FUNCTION; it will output 'myFunction'. This feature enables developers to track the flow of execution and easily identify which functions are being invoked, thus assisting in debugging and maintaining clear function logs.

The other options do not accurately represent the purpose of the FUNCTION constant. Properties of the function, the arguments passed, and the class of the function are all distinct aspects that are not returned by this constant.