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。