class in php

using class in phptoan=$toan;$this->ly=$ly;$this->hoa=$hoa;}var $tb;function tinhdiem(){$toan=$this->toan;$ly=$this->ly;$hoa=$this->hoa;$this->tb=($toan+$ly+$hoa)/3;echo "sinh vien co tong diem".$this->tb;}function xeploai(){$xl=$this->tb;if($xl<5){ echo " trung binh" ;}else if ($xl>5 &&$xl<7 ){echo " trung binh