Warning: Illegal offset type php - php

Question

I have been attempting to make a login system with php oop however I have come across this error Warning: Illegal offset type....classes\Session.php on line 11 I'm not quite sure where I'm going wrong any advice would be appreciated.
login
if(Input::exists()){
if(Token::check(Input::get('token'))){
$validate = new Validate();
$validation = $validate->check($_POST, array(
'username' => array('required' => true),
'password' => array('required' => true)
));
if ($validation->passed()){
//log user in
$user = new User();
$login = $user->login(Input::get('username'), Input::get('password'));
if($login){
echo 'Success';
}else{
echo'<p>Sorry invalid details</p>';
}
} else{
foreach($validation->errors() as $error)
echo $error, '<br />';
}
}
}
?>
<form action="" method="POST">
<div class="field">
<label for="username" id="username"> Username </label>
<input type="text" name="username" id="username" autocomplete="off">
</div>
<div class="field">
<label for="password" id="password"> Password </label>
<input type="password" name="password" id="password" autocomplete="off">
</div>
<input type="hidden" name="token" value="<?php echo Token::generate();?>">
<input type="submit" value="Login">
</form>
User
<?php
class User{
private $_db,
$_data,
$_sessionName;
public function __construct($user = null){
$this ->_db = DB::getInstance();
$this->_sessionName = Config::get('session/session_name');
}
public function create($fields = array()){
if($this->_db->insert('users', $fields)){
throw new Exception('There was a problem creating account');
}
}
public function find($user = null){
if($user){
$field = (is_numeric($user)) ? 'id' : 'username';
$data = $this->_db->get('users', array($field, '=', $user));
if($data->count()) {
$this->_data = $data->first();
return true;
}
}
return false;
}
public function login($username = null, $password = null){
$user = $this->find($username);
if($user){
if($this->data()->password ===Hash::make($password, $this->data()->salt)){
Session::put($this->_sessionName, $this-data()->id);
return true;
}
}
return false;
}
private function data(){
return $this->_data;
}
}
Session
<?php
class Session {
public static function exists($name){
return(isset($_SESSION[$name])) ? true : false;
}
public static function put($name, $value){
return $_SESSION[$name] = $value;
}
public static function get($name){
return $_SESSION[$name];
}
public static function delete($name){
if(self::exists($name)){
unset($_SESSION[$name]);
}
}
public static function flash($name, $string =''){
if(self::exists($name)){
$session = self::get($name);
self::delete($name);
return $session;
} else {
self::put($name, $string);
}
}
}
index
<?php
require_once 'core/init.php';
if(Session::exists('home')){
echo '<p>' . Session::flash('home', 'You have been registered and can now log in!') . '</p>';
}
echo Session::get(Config::get('session/session_name'));
?>

Answer 1

You should check if session key exist before trying to access it:
<?php
class Session {
public static function put($name, $value){
return $_SESSION[$name] = $value;
}
public static function get($name)
{
return self::exists($name) ? $_SESSION[$name] : null;
}
public static function exists($name)
{
return #$_SESSION[$name] !== null;
}
public static function delete($name){
if(self::exists($name)){
unset($_SESSION[$name]);
}
}
public static function flash($name, $string =''){
if(self::exists($name)){
$session = self::get($name);
self::delete($name);
return $session;
} else {
self::put($name, $string);
}
}
}