php会员管理系统

<form action="session.php" method="POST">
账  号：<input name="username" type="text" /><br><br>
密  码：<input name="password" type="password" /><br><br>
<input name="sub" type="submit" value="登录" />
</form>

<?php
session_start();
include_once ‘conn.php‘;
    $username=$_POST[‘username‘];
    $password=$_POST[‘password‘];
    $sql="select * from data where username=‘".$username."‘ and password=‘".$password."‘";
    $query=mysql_query($sql);
    $row=mysql_fetch_array($query);
    $_SESSION[‘username‘]=$username;
    $_SESSION[‘password‘]=$password;
    if (!$row){
        echo "<script language=‘javascript‘>alert(‘用户名或密码错误！‘);location=‘index.php‘;</script>";
    }else{
        echo "<script language=‘javascript‘>alert(‘登陆成功！‘);location=‘user.php‘;</script>";
    }
?>

<?php 
session_start();
if ($_SESSION[‘username‘]=="" ||$_SESSION[‘password‘==""]){
    echo "<script language=‘javascript‘>alert(‘请先登录！‘);location=‘../index.php‘;</script>";
}
?>
<?php
$user = $_SESSION[‘username‘];
$conn=mysqli_connect("localhost","root","root");
$db=mysqli_select_db($conn,"rmb");
$sql="select * from data where username=‘".$user."‘";
$re=mysqli_query($conn,$sql);
$r=mysqli_fetch_array($re);
echo "<br>";
echo "用户：".$_SESSION[‘username‘]." <a href=‘zx.php‘>退出</a><br>;


?>