php create class with no variables to pass in function -

lets have class function in it:

classes.php

 class foobar{         function writeword($word){                return $word;         }  } 

on page call class need initialize class, call later.

php2.php

require_once('classes.php'); $something = new foobar();   echo $something->writeword('dog'); 

the problem here php comes , says foobar missing arguments on line 1. how can solve this?