php登录与退出登录实例代码

function showPage() //判断是否登录 未登录直接跳转至登录页面
{
 if(!isset($_SESSION["user"]) && !isset($_SESSION["pwd"]))
 {
  if(isset($_COOKIE["user"]) && isset($_COOKIE["pwd"]))
  {
   $sql = "select * from pm_user where u_user='$_COOKIE[user]'";
   $query = mysql_query($sql);
   $isUser = is_array($row = mysql_fetch_array($query)); //判断用户名
   $isPwd = $isUser ? $row["u_pwd"] == $_COOKIE["pwd"] : false; //判断密码
   if($isPwd)
   {
    $_SESSION["user"]  = $_COOKIE["user"];
    $_SESSION["pwd"]   = $_COOKIE["pwd"];
    $_SESSION["id"]    = $_COOKIE["id"];
    $_SESSION["name"]  = $_COOKIE["name"];
   }
  }
 }
 
 if(!isset($_SESSION["user"]) && !isset($_SESSION["pwd"]))
 {
  echo '';
  exit();
 }
}

function loginOut() //登出函数
{
 if(isset($_GET["login"]) == 'out')
 {
  $_SESSION["user"]  = '';
  $_SESSION["pwd"]   = '';
  $_SESSION["id"]    = '';
  $_SESSION["name"]  = '';
  session_destroy();
  echo '';
 }
}