codeidniter 19 урок

Выдает ошибку когда в блоке

if ($slug = "movies") {
    $this->data['title'] = "Фильмы";
    $this->data['movie_data'] = $this->films_model->getFilms(false, 10, 1);
}

После $slug ставлю == 

Ошибка :

A PHP Error was encountered
Severity: Warning

Message: Invalid argument supplied for foreach()

Filename: movies/type.php

Line Number: 4

Backtrace:

File: C:\xampp\htdocs\kinomonster\application\views\movies\type.php
Line: 4
Function: _error_handler

File: C:\xampp\htdocs\kinomonster\application\controllers\Movies.php
Line: 29
Function: view

File: C:\xampp\htdocs\kinomonster\index.php
Line: 315
Function: require_once

Код :

1)Movies.php

public function type($slug = NULL) {
$this->data['movie_data'] = null;

if ($slug == "movies") {
$this->data['title'] = "Фильмы";
$this->data['movie_data'] = $this->films_model->getFilms(false, 10, 1);
}

if ($slug == "serials") {
$this->data['title'] = "Сериалы";
$this->data['movie_data'] = $this->films_model->getFilms(false, 10, 2);
}

/*if ($this->data['movie_data'] == null) {
show_404();
}*/

$this->load->view('templates/header', $this->data);
$this->load->view('movies/type', $this->data);
$this->load->view('templates/footer');
}

2)type.php

<h3><?php echo $title; ?></h3>
<hr>

<?php foreach ($movie_data as $key => $value): ?>
<div class="row">
<div class="well clearfix">
<div class="col-lg-3 col-md-2 text-center">
<img class="img-thumbnail" src="<?php echo $value['poster']; ?>" alt="<?php echo $value['name']; ?>">
<p><?php echo $value['name']; ?></p>
</div>
<div class="col-lg-9 col-md-10">
<p>
<?php echo $value['descriptions']; ?>
</p>
</div>
<div class="col-lg-12">
<a href="/movies/view/<?php echo $value['slug']; ?>/" class="btn btn-lg btn-warning pull-right">Подробнее</a>
</div>
</div>
</div>
<?php endforeach ?>