PHP通过id从数据库回显

Question

How do I echo a user's name and his specific country? Like this:

Account name: leo

Country: Germany

The account name is working.

PHP at the top of the page is:

<?php 
    session_start(); 

    if (!isset($_SESSION['username'])) {
        $_SESSION['msg'] = "You must log in first";
        header('location: login.php');
    }

    if (isset($_GET['logout'])) {
        session_destroy();
        unset($_SESSION['username']);
        header("location: login.php");
    }
?>

Connect to database (seperate file server.php):

$db = mysqli_connect('localhost', 'root', '', 'registration');

HTML:

<li class="p-li">Account name: <?php echo $_SESSION['username']; ?></li>
<li class="p-li">Country:<?php echo $_a['a']; ?> </li>

Answer 1

You need to define $_a at the moment it doesn't appear to be referencing anything so would be blank. Forgetting that though you asked about SQL query in the comments.

SQL Query would be

$id = $_SESSION['username'];   

"SELECT Country FROM registration WHERE username='%".id."%'"

Please be aware that's just a snippet of code as you said you wanted the SQL query. I defined $id as the users username as you said you wanted to get country by username, I would though recommend you use the id column of the table as this will always be unique.