$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
$id = $_GET['id'];
if($id != null)
    $sql = "SELECT * FROM users WHERE id=".$id."";
else
    $sql = "SELECT * FROM users";
$result = $conn->query($sql);

if ($result->num_rows > 0 && $id == null) {
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " Name: " . $row["name"].""."<br>";
    }
} else if($id == null) {
    echo "0 results";
}else{
    while($row = $result->fetch_assoc()) {
    echo "id: " . $row["id"]. "-Name: " . $row["name"]."-Email: ".$row["email"]."-Pass: " . $row["pwd"]."-Sex: " . $row["sex"]."<br>";
    }
}
$conn->close();