登陸界面限制到只允許一臺機器在線

<?php
ob_start();
session_start();
class CC{
    private $REFURL="http://www.abc.com";        //登陸成功后轉換頁面
    private $LoginFLAG=false;                //登陸成功標志
    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){//用戶登陸存在而且有效
            $info=file($this->loginFILE);
            $username=trim($info[0]);    //已在線的登陸用戶名
            $password=trim($info[1]);    //已在線密碼（可以不保存）
            $ip     =trim($info[2]);    //已在線IP
            $sid     =trim($info[3]);    //已在線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>您的帳戶可以確定是唯一的！</h3>";
                            $cf=fopen($this->loginFILE,"a+");
                            fputs($cf,"\r\na");
                            fclose($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 "不允許帳戶在局網上同時登陸.. ".$_SERVER[REMOTE_PORT];
                            $this->LoginFLAG=false;
                        }                
                    }else{
                        echo "不允許使用帳戶同時登陸..<br>";
                            $this->LoginFLAG=false;
                    }
                }else{
                    echo "密碼錯誤..<br>";
                    $this->LoginFLAG=false;
                }
            }else{
            //這里驗證身份如果正確則
                echo "帳戶登陸時發生錯誤！用戶名錯誤<br><pre>";
            }
        }else{
            if(isset($_POST[LoginUser])){
                $_SESSION[LoginUser]=$_POST[LoginUser];
                $_SESSION[LoginPw]=$_POST[LoginPw];
                $fp=fopen($this->loginFILE,"w");
                $msg=$_POST['LoginUser']."\r\n".$_POST['LoginPw']."\r\n".$_SERVER[REMOTE_ADDR]."\r\n".session_id();;
                fputs($fp,$msg);
                fclose($fp);
            }else{
                $outtime=time()-filemtime($this->loginFILE)-60;
                echo "登陸不存在或您已經超時(".$outtime."秒)...";
            }
        }
    }
    function Wfrom(){
    global $_POST;
    if(!file_exists($this->loginFILE) ||(time()-filemtime($this->loginFILE))>60){        //登陸失敗
    echo <<<LOGINFORM
    <Form action="$_SERVER[PHP_SELF]" method="post" name="Loginform">
        <table cellpadding=0 border=0>
        <tr><td>
        用戶名：<td><input type="text" name="LoginUser"></span><br>
        <tr><td>密碼：<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 "已有用戶登陸";
    }
    }
}
$D=new CC;
$D->check();
$D->Wfrom();
?>

原文轉自：http://www.anti-gravitydesign.com