How to call mysqli query in a function

function get_user_data($user_id) {
    $mysqli = new mysqli("localhost", "username", "password", "database");

    if ($mysqli->connect_errno) {
        return "Failed to connect to MySQL: " . $mysqli->connect_error;
    }

    $sql = "SELECT * FROM users WHERE id = ?";
    $stmt = $mysqli->prepare($sql);
    $stmt->bind_param("i", $user_id);
    $stmt->execute();
    $result = $stmt->get_result();

    if (!$result) {
        return "Error executing query: " . $mysqli->error;
    }

    $data = array();

    while ($row = $result->fetch_assoc()) {
        $data[] = $row;
    }

    $stmt->close();
    $mysqli->close();

    return $data;
}

// Example usage
$user_data = get_user_data(123);

if (is_array($user_data)) {
    foreach ($user_data as $row) {
        echo $row["username"] . "<br>";
    }
} else {
    echo $user_data;
}