Preserving $_POST variables when paginating - php

Question

I have a simple list of orders which a user can filter by status (open,dispatched,closed). The filter dropdown triggers a post to the server and sends the filter value through. Orders are listed out 10 to a page with pagination links for any results greater than 10. Problem is when I click the pagination links to view the next page of results the filter value in the post is lost.
public function filter_orders() {
$page = ($this->uri->segment(4)) ? $this->uri->segment(4) : 0;
$filter = $this->input->post('order_status_filter');
$config = array();
$config["base_url"] = base_url() . "control/orders/filter_orders";
$config["per_page"] = 10;
$config['next_link'] = 'Next';
$config["uri_segment"] = 4;
$config['total_rows'] = $this->model_order->get_all_orders_count($this->input->post('order_status_filter'));
}
How can I make the pagination and filter work together. I've thought about injecting a query string in to the pagination links but it doesn't seem like a great solution.

Answer 1

The answer is very simple, use $_GET. You can also use URI segments.
i.e, index.php/cars/list/5/name-asc/price-desc'
The main reason you'll want to use $_GET is so you can link other users so they see the same result set you see. I'm sure users of your web app will want this functionality if you can imagine them linking stuff to each other.
That said, it would be ok to ALSO store the filters in the session so that if the user navigates away from the result set and then goes back, everything isn't reset.

Answer 2

Your best bet is to start a session and store the POST data in the session. In places in your code where you check to see if the user has sent POST data, you can check for session data (if POST is empty).
In other words, check for POST data (as you already do). If you got POST data, store it in the session. If a page has no POST data, check to see if you have session data. If you do, proceed as if it was POSTed. If you have both, overwrite the session with POST. You'll want to use new data your user sent you to overwrite older data they previously sent.

Answer 3

You either put everything in $_GET or if the data is sensible, put it in $_SESSION. Then it travels between pages.
In your case there seem to be no reason to put your filter data anywhere else than in $_GET.

Answer 4

A query string does seem the best solution. You could store it in the session or in cookies as well, but it makes sense to also store it in the query string.
Store it in cookies or the session if you want to remember the user's choice. Which seems like a friendly solution. It allows the user to keep their settings for a next visit, or for another page.
Store it in the query string, because going to 'page 2' doesn't tell you anything if you don't know about filters, page size or sorting. So if a user wants to bookmark page 2 or send it by e-mail, let them be able to send a complete link that contains this meta information.
Long story short: Store it in both.

Answer 5

maybe its not a right answer but, give it a try
<?php
// example url
$url = "index.php?page=6&filter1=value1&filter2=value2";
// to get the current url
//$url = "http://".$_SERVER["HTTP_HOST"].$_SERVER["REQUEST_URI"];
// change the page to 3 without changing any other values
echo url_change_index( $url, "page", 3 );
// will output "index.php?page=3&filter1=value1&filter2=value2"
// remove page index from url
echo url_change_index( $url, "page" );
// will output "index.php?filter1=value1&filter2=value2"
// the function
function url_change_index( $url, $name = null, $value = null ) {
$query = parse_url( $url, PHP_URL_QUERY );
$filter = str_replace( $query, "", $url );
parse_str( $query, $parsed );
$parsed = ( !isset( $parsed ) || !is_array( $parsed ) ) ? array() : $parsed;
if ( empty( $value ) ) {
unset( $parsed[$name] );
}
else {
$parsed[$name] = $value;
}
return $filter.http_build_query( $parsed );
}
?>