PHP MySQLi num rows Always Returns 0

Question

In order to make database interaction simpler, I created a class that makes use of MySQLi, a built-in PHP class. I am having trouble getting the num rows instance variable to produce the correct amount of rows after a query is done, though, using an OOP method. Check out this picture of my class...

Why is this incorrect, though? Other numbers from the result object, like "field count," are correct. I sincerely appreciate any assistance.