How do I show the username instead of the email

See more:

PHP

MySQL

Hello I'm trying to show the users username instead of the user email but I can't seem to get that working why can I only use $_SESSION['email'];?

code login

<pre><?php
session_start();
// Check if the user is already logged in, if yes then redirect him to welcome page
if(isset($_POST["email"]) && $_POST["password"] === true){
    header("location: welcome.php");
    exit;
}

 // Include config file
include "config.php";

if ($_SERVER['REQUEST_METHOD'] === 'POST') { 
    $email = mysqli_real_escape_string($conn , $_POST['email']);
    $password = mysqli_real_escape_string($conn , $_POST['password']);

    // link voor de prepared statemts met select https://stackoverflow.com/questions/60174/how-can-i-prevent-sql-injection-in-php
    $sql  = 'SELECT * FROM users WHERE email = ?';
    $stmt = $conn->prepare($sql); 
    $stmt->bind_param("s", $email);
    $stmt->execute();
    $result = $stmt->get_result(); // get the mysqli result
    if ($row = $result->fetch_assoc()) {
        if (password_verify($password, $row['password'])) {
                        // login
                        $_SESSION['loggedin'] = true;
                        $_SESSION['ID'] = $row['ID'];
                        $_SESSION['username'] = $row['username'];
                        $_SESSION['name'] = $row['name'];
                        $_SESSION['email'] = $email;
                        header("Location: welcome.php");
            }else {
                $message = "Invalid password or username";
                echo '<script language="javascript">';
                echo "alert('$message');\n";
                echo 'window.location.href="login.php"'; //Redirects the user with JavaScript
                echo '</script>';
            }
            
        $conn->close();
    }else{
        $message = "Invalid password or username";
        echo '<script language="javascript">';
        echo "alert('$message');\n";
        echo 'window.location.href="login.php"'; //Redirects the user with JavaScript
        echo '</script>';
    }
}
 ?>

this is where I want to greet people

<?php 
session_start();
if(!isset($_SESSION['id'])){

//if (isset($_SESSION['loggedin']) && $_SESSION['username'] == $username) {
    echo "Welcome to the member's area, " . $_SESSION['email'] . "!";
}

Like I said $_SESSION['email']; shows up just fine but $_SESSION['username']; doesn't show up why is this happening?

What I have tried:

Tried looking a few times on the internet
used stack overflow
but because english is not my first language its is pretty hard to type into google what I need