Defining and calling functions in PHP Mocktest

Nested functions in PHP allow defining functions within other functions, enabling encapsulation and modularization of code by restricting the scope of inner functions to their parent functions.

The output of the code will be Function does not exist: inner because the inner function inner() is defined within the outer() function and is not accessible outside of it. Attempting to call inner() directly results in an error since it is not defined in the global scope.