Retrieve data from database by class - php

Question

I would like to learn programming, so I downloaded a safe script built in OOP to manage the login and user registration, I would like to get their hands to learn this language through classes and objects.
The script is this: https://github.com/aguvasu/Secure-PHP-OOP-user-reg-login-system-with-Boostrap
I come down to it, my problem where I can not find solution is that I would like to create a page where member.php show the list of registered users (username, email, etc.), but do not know how to do.
The class User.php shows this:
class User {
private $_db, $_data, $_sessionName, $_cookieName, $_isLoggedIn;
function __construct($user = null) {
$this->_db = DB::getInstance();
$this->_sessionName = Config::get('session/session_name');
$this->_cookieName = Config::get('remember/cookie_name');
if (!$user) {
if (Session::exists($this->_sessionName)) {
$user = Session::get($this->_sessionName);
if ($this->find($user)) {
$this->_isLoggedIn = true;
} else {
//logout
}
}
} else {
$this->find($user);
}
}
public function find($user = null) {
if ($user) {
$field = (is_numeric($user)) ? 'id' : 'username' ;
$data = $this->_db->get('users', array($field, '=', $user));
if ($data->count()) {
$this->_data = $data->first();
return true;
}
}
return false;
}
public function create($fields = array()) {
if (!$this->_db->insert('users', $fields)) {
throw new Exception("Error Processing Request", 1);
}
}
public function login($username = null, $password = null, $remember = null) {
if (!$username && !$password && $this->exists()) {
Session::put($this->_sessionName, $this->data()->id);
} else {
$user = $this->find($username);
if ($user) {
if ($this->data()->password === Hash::make($password, $this->data()->salt)) {
Session::put($this->_sessionName, $this->data()->id);
if ($remember) {
$hash = Hash::unique();
$hashCheck = $this->_db->get('users_sessions', array('user_id', '=', $this->data()->id));
if (!$hashCheck->count()) {
$this->_db->insert('users_sessions', array(
'user_id' => $this->data()->id,
'hash' => $hash));
} else {
$hash = $hashCheck->first()->hash;
}
Cookie::put($this->_cookieName, $hash, Config::get('remember/cookie_expiry'));
}
return true;
}
}
}
return false;
}
public function update($fields = array(), $id = null) {
if (!$id && $this->isLoggedIn()) {
$id = $this->data()->id;
}
if (!$this->_db->update('users', $id, $fields)) {
Session::flash('uperr', 'We experienced an error while updating your profile');
Redirect::to('account.php');
exit();
}
}
public function hasPermission($key) {
$group = $this->_db->get('groups', array('id', '=', $this->data()->user_group));
if ($group->count()) {
$permissions = json_decode($group->first()->permissions, true);
if ($permissions[$key]) {
return true;
}
}
return false;
}
public function logout() {
$this->_db->delete('users_sessions', array('user_id', '=', $this->data()->id));
Session::delete($this->_sessionName);
Cookie::delete($this->_cookieName);
}
public function data() {
return $this->_data;
}
public function isLoggedIn()
{
return $this->_isLoggedIn;
}
public function exists() {
return (!empty($this->_data)) ? true : false ;
}
}