[CodeIgniter]libraries目錄中class內函數互相呼叫

class Myclass {

public function js_alert($str1,$str2='')
{ 
echo "<meta http-equiv=Content-Type content=text/html; charset=utf-8>";
if($str2=='')
{echo "<script>alert('$str1');history.go(-1);</script>";exit();}
else
{echo "<script>alert('$str1');location.href='$str2';</script>";exit();}
exit();
}


//後台帳號檢查
public function is_power_check()
{
     @session_start();    
     if(empty($_SESSION['id']))
     {$this->js_alert('請先登入','../manage/login');}
}


}