mysql和php-根据登录的用户从数据库中检索数据

Question

before I go ahead and attempt to create a website, I wanted to know if pulling a users content from a database depending on which user is logged in can be determined by a $_SESSION variable. So for example if I want all the messages for user 'example':

$_SESSION['username'] = $_POST['username'] // set when the user logs in
$username = $_SESSION['username']

$data = mysql_query("Select * from messagesTable where username = '$username'")
while($row = mysql_fetch_array($data)) {
echo $row['message']
}

I wanted to know if this would be the right way to do something like this and also if its safe to return (personal) data based on a session variable.

I haven't got that much experience in either of these languages but I like to learn with experience, please tell me if it's not clear. Thanks.

Answer 1

It is safe to return user data based on a $_SESSION variable if you are certain of its validity because you set it yourself in code. It is not safe to return data based on a session variable that you get from $_POST .

You initially set

$_SESSION['username'] = $_POST['username'];

So unless you have verified with a password or otherwise that this user is who he claims to be, you should not use $_POST['username'] to return other information. If your login process (which we cannot see above) already verifies that $_POST['username'] is valid, you can use it as a source to retrieve additional information.

You will need also to filter against SQL injection:

$_SESSION['username'] = mysql_real_escape_string($_POST['username']);

Answer 2

这不是标准的，并且可能不安全，因为即使无法打开浏览器选项卡，phpsession仍保持打开状态，因为直到关闭浏览器后cookie才会缓和，您也可以将post参数发送到网站，并且也可以获取信息，因此登录脚本要高级一些，您可以像具有在登录时生成的唯一键，当它们使用javascript离开站点时删除Cookie之类的东西。

Answer 3

It wouldnt be the correct way to do it no.

May i suggest you go read the php/mysql docs and or a good book before attempting a website.

You also need to look into security(session hijacking, cross scripting, mysql attacks, form tokens, login systems, user roles/permissions). Google search is your friend...

Answer 4

<?php
session_start();
    $username="";
    if($_SESSION['username']==true){
            $username=$_SESSION['username'];
            $conn=mysql_connect('localhost','user','passwd') or die("Unable   
                   to connect to database" .mysql_error());
            mysql_select_db('DBName') or die(mysql_error());
            $sql="SELECT * FROM tablename WHERE username='$username'";
            $retval=mysql_query($sql, $conn) or die("Could not perform query" 
              .mysql_error());
            while($row=mysql_fetch_array($retval)){
                echo {$row['message']};
            }
            mysql_free_result($retval);
            mysql_close($conn);
    }
    else{
        return false;
        header("Location:login.php");
    }
?>