PHP 实现一个账号仅允许一个用户登陆

测试的SQL语句

CREATE TABLE IF NOT EXISTS `tb_user` (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '编号',
  `username` varchar(80) NOT NULL COMMENT '用户',
  `pwd` varchar(80) NOT NULL COMMENT '密码',
  `session_id` varchar(50) DEFAULT NULL COMMENT '一个账号只能登录一次',
  `create_time` datetime NOT NULL COMMENT '创建时间',
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COMMENT='用户表' AUTO_INCREMENT=2 ;

INSERT INTO `tb_user` (`id`, `username`, `pwd`, `session_id`, `create_time`) VALUES
(1, 'chaoyi', '123456', 'sab3s49pnciq6vmlqeiuc6e0g0', '2017-06-02 00:00:00');

登陆页面：

<?php
header('Content-Type: text/html; charset=utf-8');
define('CHAOYI',true);
require "/includes/connect.inc.php";

//判断是否是POST提交过来的数据
if($_SERVER["REQUEST_METHOD"] == "POST" && isset($_POST['userForm'])){
	session_start();
	$username = trim($_POST["username"]);
	$password = trim($_POST["password"]);
	$sqluser = "SELECT * FROM tb_user WHERE username='$username' AND pwd='$password' ORDER BY id DESC LIMIT 1";
	$result = sqlGetOne($sqluser);
	
	//如果没有取到数据，则判断账号密码不正确
	if(empty($result['id'])){
		session_destroy();
		sqlClose();
		echo "<script type='text/javascript'>alert('用户名和密码不正确，登陆失败！');window.location.href='logo.php';</script>"; 
		exit;
	}
	
	//获取 session ID
	$session_id = session_id();
	$sqlupdatauser = "UPDATE tb_user SET session_id = '$session_id' WHERE id = '{$result['id']}'";
	sqlQuery($sqlupdatauser);
	
	//存在一些共享数据到 session 里
	$_SESSION['id'] = $result['id'];
	$_SESSION['username'] = $result['username'];
	$_SESSION['session_id'] = $session_id;
	
	sqlClose();
	echo "<script type='text/javascript'> window.location.href='admin.php';</script>"; 
	exit;	
}
?>
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<title>登陆页面</title>
</head>
<body>

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
<p>姓名：<input type="text" name="username"></p>
<p>密码：<input type="password" name="password"></p>
<input type="submit" name="userForm" value="提交" />
</form>

</body>
</html>

效果图：

管理页面：

<?php
header('Content-Type: text/html; charset=utf-8');
define('CHAOYI',true);
require "/includes/connect.inc.php";
session_start();
if(isset($_SESSION['id']) && isset($_SESSION['username']) && isset($_SESSION['session_id'])){
	$session_id = session_id();
	$sqluser = "SELECT id FROM tb_user WHERE id='{$_SESSION['id']}' AND session_id='$session_id' ORDER BY id DESC LIMIT 1";
	$result = sqlQuery($sqluser);	
	$resRows = mysql_num_rows($result);

	if($resRows == false){
		sqlClose();
		echo "<script type='text/javascript'> alert('对不起，你的帐号在其他地方登陆了！'); window.location.href='logout.php';</script>";
		exit;
	}
}else{
	sqlClose();
	echo "<script type='text/javascript'> alert('请登陆你的账号密码'); window.location.href='logo.php';</script>";
	exit;
}
?>
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<title>管理页面</title>
</head>
<body>

<h3 style="text-align: center;">用户名：<?php echo $_SESSION['username'];?></h3>
<h3 style="text-align: center;">Session ID： <?php echo $_SESSION['session_id'];?></h3>
<h4 style="text-align: center;"><a href="logout.php">注销</a></h4>

</body>
</html>

效果图：

注销页面：

<?php
header('Content-Type: text/html; charset=utf-8');
define('CHAOYI',true);
require "/includes/connect.inc.php";
session_start();

//注销 session
unset($_SESSION['id']);
unset($_SESSION['username']);
unset($_SESSION['session_id']);
session_destroy();

sqlClose();
echo "<script type='text/javascript'>window.location.href='logo.php';</script>";
exit;

PHP 实现一个账号仅允许一个用户登陆

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