Question from the PHP7 test

__toString() 'is a class method that determines how the object should react if it is treated as a string.

__referTo() 'is a class method that determines how the object should react if it is used as a' bridge 'with another class.

__isset() 'is a class method called when the isset() or empty() functions are called on inaccessible properties. '

__set() 'is a class method that defines how the object should react if a method is not accessible.

__call() 'is a class method that defines how the object should react if a static context method is unreachable.