Solution: Apply the factory pattern

- In this solution, we didn't have…to modify index.php at all.…Instead, all of our work is in the shapes.php file.…In this solution, we went with a K statement.…Since there are only two options,…we could have used an if else,…but odds are we'll get more shapes,…so we might as well think of this now.…Further, we have a number of exit points to this function.…In some languages this is problematic,…but in PHP there are no issues with it.…In fact, by returning immediately,…we're less likely to hit other issues…such as a forgotten break statement, or similar.…Our circle and square classes are pretty simple, too.…Their constructors are essentially identical,…we're just capturing the incoming value…and storing it for later.…

Then our get area method calculates the area…according to what you'd expect.…There's one potential issue here.…Since the radius and side are protected values,…we don't have a way outside the constructor to modify them.…These objects are immutable, or unchangeable.…If we need to modify a circle or square, we'll actually have…