Random SQL record while excluding specific records - php

Question

I have a CodeIgniter PHP application that shows two movie covers. Beside them is a "random movie" button that uses AJAX to replace the two movies with a new set of movies. You can continue to click this, over and over, and see it continue to replace the images of the movie covers. The first two covers to show are set as the defaults, and they should never show after the user has clicked the random movie button. The problem is this: When clicking the random movie button, it will some times take many clicks to finally show a new cover. That is, the same cover will be returned multiple times in a row. The two different covers being fetched are being called from slightly different URLs, so they will rarely both break at the same time. This lets me know that it is refreshing, but that the function is returning the same movie multiple times. If I access the url that is being called via AJAX directly, I never see this take place since I have used the Session class to store the last movie's and exclude it from the SQL query (i.e. WHERE id NOT IN ($default_movie, $last_movie)). Any idea why accessing the url directly would work fine, but when calling via AJAX, I'm seeing this behavior?
I know this may not have been as clear as possible, so let me know if I can clarify something that doesn't make sense. I'll add code if that helps as well. Thanks friends!
Query to get random movie:
SELECT * FROM (`movies`) WHERE `id` NOT IN (2, 10) ORDER BY RAND() LIMIT 1
Model method:
public function getRandom($count = 1, $featured = FALSE, $series = FALSE, $exclude = 0, $last = 0) {
$this->db->order_by('id', 'random');
$this->db->limit(1);
$conditions = array();
if ($exclude > 0) {
$conditions['id !='] = $exclude;
}
if ($last > 0) {
if (!empty($conditions['id !='])) {
$conditionsNotIn = "id NOT IN (" . $conditions['id !=']. ", $last)";
unset($conditions['id !=']);
$this->db->where($conditionsNotIn);
} else {
$conditions['id !='] = $last;
}
}
if ($featured) {
$conditions['featured'] = 1;
}
if ($series) {
$conditions['current_series'] = 1;
}
$movie = $this->db->get_where('movies', $conditions);
$movie = $movie->row();
if (!is_null($movie)) {
return $movie;
} else {
return FALSE;
}
}

Answer 1

Any idea why accessing the url directly would work fine, but when
calling via AJAX, I'm seeing this behavior?
I have an idea yes.
Browser caching.. PITA!
Try turning off caching explicitly:
$.ajaxSetup({cache: false});
Put that before your ajax request, assuming you're using jQuery.
If you're not you need to append some random variable to the url, this keep the browser from caching the requests.