Getting Undefined index: username in, and also require_once(classes/Tokin.php): failed to open stream: No such file or directory in

Question

I am following a tutorial and doing exactly everything the same. I'm not sure if I just have a typo somewhere or what, but at this point I am completely lost. I made a form and it is giving me multiple errors when I try to put a value field in to remember the value I typed in. Here is the page source since the console is not showing errors. I will provide will all the pages required to help.

ANSWER EDIT: I have found out the problem for all the errors. The first error I get is Undefined index: username in .... So to fix that in the input.php class I made. for the Input::get() function where it says if(isset($_POST)) you just need to rewrite that if(isset($_POST[$item])), I had help and this is not checking for posted data just so you need to add the '$item' so it checks for the 'username'. Then I had misspelled token in the form as tokin. So that fixed the require_once(classes/Toki(should be e not i)n.php) problem.

<form action="" method="post">
  <div class="field">
    <label for="username">Username</label>
    <input type="text" name="username" id="username" value="<br />
<b>Notice</b>:  Undefined index: username in <b>C:\xampp\htdocs\PHP_Registration_Login\classes\Input.php</b> on line <b>23</b><br />
" autocomplete="off">
  </div>
  <div class="field">
    <label for="password">Choose a password</label>
    <input type="password" name="password" id="password" value="">
  </div>
  <div class="field">
    <label for="password_again">Confirm password</label>
    <input type="password" name="password_again" id="password_again" value="">
  </div>
  <div class="field">
    <label for="name">Name</label>
    <input type="text" name="name" id="name" value="<br />
<b>Notice</b>:  Undefined index: name in <b>C:\xampp\htdocs\PHP_Registration_Login\classes\Input.php</b> on line <b>23</b><br />
">
  </div>

  <input type="hidden" name="token" value="<br />
<b>Warning</b>:  require_once(classes/Tokin.php): failed to open stream: No such file or directory in <b>C:\xampp\htdocs\PHP_Registration_Login\core\init.php</b> on line <b>22</b><br />
<br />
<b>Fatal error</b>:  require_once(): Failed opening required 'classes/Tokin.php' (include_path='.;C:\xampp\php\PEAR') in <b>C:\xampp\htdocs\PHP_Registration_Login\core\init.php</b> on line <b>22</b><br />

Here is init.php

<?php
session_start();

$GLOBALS['config'] = array(
  'mysql' => array(
    'host' =>  '127.0.0.1',
    'username' => 'root',
    'password' => 'root',
    'db' => 'register_login'
  ),
  'remember' => array(
    'cookie_name' => 'hash',
    'cookie_expiry' => 604800
  ),
  'session' => array(
    'session_name' => 'user',
    'token_name' => 'token'
  )
);

spl_autoload_register(function($class) {
  require_once 'classes/' . $class . '.php';
});

require_once 'functions/sanitize.php';
 ?>

Here is register.php

<?php
require_once 'core/init.php';

if(Input::exists()){
  if(Token::check(Input::get('token'))){
    $validate = new Validate();
    $validation = $validate->check($_POST, array(
      'username' => array(
        'required' => true,
        'min' => 2,
        'max' => 20,
        'unique' => 'users'
      ),
      'password' => array(
        'required' => true,
        'min' => 6
      ),
      'password_again' => array(
        'required' => true,
        'matches' => 'password',
      ),
      'name' => array(
        'required' => true,
        'min' => 2,
        'max' => 50
      )
    ));

    if($validation->passed()) {
      Session::flash('success', 'You registered successfully!');
      header('Location: index.php');
    } else {
      foreach($validation->errors() as $error){
        echo $error, '<br>';
      }
    }
  }
}
?>

<form action="" method="post">
  <div class="field">
    <label for="username">Username</label>
    <input type="text" name="username" id="username" value="<?php echo escape(Input::get('username')); ?>" autocomplete="off">
  </div>
  <div class="field">
    <label for="password">Choose a password</label>
    <input type="password" name="password" id="password" value="">
  </div>
  <div class="field">
    <label for="password_again">Confirm password</label>
    <input type="password" name="password_again" id="password_again" value="">
  </div>
  <div class="field">
    <label for="name">Name</label>
    <input type="text" name="name" id="name" value="<?php echo escape(Input::get('name')); ?>">
  </div>

  <input type="hidden" name="token" value="<?php echo Tokin::generate(); ?>">
  <input type="submit" value="Sign Up">
</form>

Here is input.php

<?php

class Input {


  public static function exists($type = 'post') {
    switch($type) {
      case 'post';
        return (!empty($_POST)) ? true : false;
      break;
      case 'get';
        return (!empty($_GET)) ? true : false;
      break;
      default:
        return false;
      break;
    }
  }


  public static function get($item){
    if(isset($_POST)){
      return $_POST[$item];
    } elseif(isset($_GET)) {
        return $_GET[$item];
    }
    return '';
  }

}

Here is Token.php

class Token {
  public static function generate() {
    return Session::put(Config::get('session/token_name'), md5(uniqid()));
  }

  public static function check($token) {
    $tokenName = Config::get('session/toke_name');

    if(Session::exists($tokenName) && $token === Session::get($tokenName)){
      Session::delete($tokenName);
      return true;
    }
    return false;
  }
}

And here is Session.php since Token.php uses it

<?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() {
    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);
    }
  }


}