用相同的用户名php显示结果

I have a database which stores data. How can I view data in my database with the same username as my session? What I have tried is below. There is a session and the username is uploading in each row in the database.

This is what I'm trying to do: say I logged in as jack I typed data in and sent it to the database. It saves the name as jack and then only views the results with jack. But it is saying 0 results. Why?

<?php
session_start();
if (isset($_SESSION['username'])) {
    $username = $_SESSION['username'];
    echo "$username";
}

$servername = "localhost";
$username = "root";
$password = "root";
$dbname = "score";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "SELECT id, name, description FROM all_scores WHERE username = '".$username."' ORDER BY id DESC LIMIT 5";
$result = $conn->query($sql);

if ($result->num_rows > 0) {    
    while($row = $result->fetch_assoc()) {
        echo "<p></p>";
        echo "<a href=score_2/view.php?pageid=" . $row["id"] . ">". $row["name"]. "</a>";
        echo "<p>". $row["description"]. "</p>";
    }
} else {
    echo "0 results";
}

$conn->close();

?>

you have two mistakes

1- SQL syntax error, correct syntax is

$sql = "SELECT id, name, description FROM all_scores WHERE username = '".$username."'";

2- the variable $username is overwritten by the username of the database try this:

$sql = "SELECT id, name, description FROM all_scores WHERE username = '".$_SESSION['username']."'";