php类与对象简单操作

<?php
/*
 * Created on 2015-8-25
 *
 * To change the template for this generated file go to
 * Window - Preferences - PHPeclipse - PHP - Code Templates
 */
 class Type{

    var $username;
    public function getUserName(){

        return $this->username;

    }
    public function setUserName($username){
        $this->username = $username;

    }

 }
 class Free{
     private static $username;
     public static function getUser(){
         return Free::$username;
     }
     public static  function setUser($username){
         Free::$username = $username;

     }

 }
 $user = "link";
 Free::setUser($user);
 echo Free::getUser();
 $type = new Type();
 $type->setUserName("zhangming");
 echo $type->getUserName();
?>

初学php，望大家能多多纠正错误。