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);
 }