登陆界面限制到只允许一台机器在线

<?php
ob_start();
session_start();
class CC{
private $REFURL="http://www.abc.com";        //登陆成功后转换页面
private $LoginFLAG=false;                //登陆成功标志
private $loginFILE="loginmsg.txt";            //信息文件

function setFlag($flag){
$this->loginFLAG=$flag;
}
function check(){
global $_POST;
if(file_exists($this->loginFILE)&& (time()-filemtime($this->loginFILE))<60){//用户登陆存在而且有效
$info=file($this->loginFILE);
$username=trim($info[0]);    //已在线的登陆用户名
$password=trim($info[1]);    //已在线密码（可以不保存）
$ip     =trim($info[2]);    //已在线IP
$sid     =trim($info[3]);    //已在线PORT
if(strcmp($_SESSION[LoginUser],$username)==0){
if(strcmp($_SESSION['LoginPw'],$password)==0){
if(strcmp($_SERVER[REMOTE_ADDR],$ip)==0){
if(strcmp(session_id(),$sid)==0){
$this->setFlag(true);
echo "<h3>您的帐户可以确定是唯一的！</h3>";
$cf=fopen($this->loginFILE,"a+");
fputs($cf,"rna");
fclose($cf);
echo "<meta http-equiv=refresh content="10;url=t.php">";
//echo "<iframe src="t.php" frameborder=0 width=0 height=0></iframe>";
}else{
echo "不允许帐户在局网上同时登陆.. ".$_SERVER[REMOTE_PORT];
$this->LoginFLAG=false;
}                
}else{
echo "不允许使用帐户同时登陆..<br>";
$this->LoginFLAG=false;
}
}else{
echo "密码错误..<br>";
$this->LoginFLAG=false;
}
}else{
//这里验证身份如果正确则
echo "帐户登陆时发生错误！用户名错误<br><pre>";
}
}else{
if(isset($_POST[LoginUser])){
$_SESSION[LoginUser]=$_POST[LoginUser];
$_SESSION[LoginPw]=$_POST[LoginPw];
$fp=fopen($this->loginFILE,"w");
$msg=$_POST['LoginUser']."rn".$_POST['LoginPw']."rn".$_SERVER[REMOTE_ADDR]."rn".session_id();;
fputs($fp,$msg);
fclose($fp);
}else{
$outtime=time()-filemtime($this->loginFILE)-60;
echo "登陆不存在或您已经超时(".$outtime."秒)...";
}
}
}
function Wfrom(){
global $_POST;
if(!file_exists($this->loginFILE) ||(time()-filemtime($this->loginFILE))>60){        //登陆失败
echo <<<LOGINFORM
<Form action="$_SERVER[PHP_SELF]" method="post" name="Loginform">
<table cellpadding=0 border=0>
<tr><td>
用户名：<td><input type="text" name="LoginUser"></span><br>
<tr><td>密码：<td><input type="password" name="LoginPw"></span><br>
<tr><td> <td><input type="button" value=" Login " onclick="if(this.form.LoginUser.length*this.form.LoginPw.length!=0){this.form.submit();}else{return false;}">
</table>
</form>
LOGINFORM;
}else{
echo "已有用户登陆";
}
}
}
$D=new CC;
$D->check();
$D->Wfrom();
?>