Creating a PHP Class won't allow me to use control statements

I have a pretty simple question so it seems. I am creating a class, in which I have a public function that takes an input. Inside of the function, I want to use and if statement to determine if the value is larger or smaller than a class property. When I begin to type the IF statement in my IDE (Aptana) it gives me a syntax error. I am new at PHP, so if anyone could point me in the right direction, I would appreciate it.