php 用户登陆代码，入门教程

php 用户登陆代码，入门教程
 function login_xzy()
 {
  $user_=db("user");
  $session_=db("session");
  $login['email']=strip_tags($_POST['email']);
  $login['pass']=empty($_POST['pass'])?"":md5($_POST['pass']);
  if($user=$user_->where("`email`='{$login['email']}' and `pass`='{$login['pass']}'")->find()){
   if($session_->where("`uid`='{$user['uid']}'")->find()){
    $json['status']=1;
    $json['info']='已登陆的会员!';
   }else{
    $user['total']++;
    $user_->where("`uid`='{$user['uid']}'")->update(array('total'=>$user['total'],'lastip'=>ip2long(getip()),'lasttime'=>time() ));
    $session_->where("session_id='".Session_id()."'")->update(array('uid'=>$user['uid']));
    $_SESSION['user']=$user;
    $json['data']=$user;
    $json['status']=0;
   }
  }else{
   $json['status']=1;
   $json['info']='用户名或密码不正确!';
  }
  echo json_encode($json);
 }