使用json加载更多功能

Question

I am trying to implement a load more feature in a web app I am building. When the app loads, it makes an ajax call to controller which retrieves the data from the database and then encodes them in JSON. I am making use of limits and offsets in mysql query and I more data to be loaded as the user scrolls down. This is the method in the controller which the ajax call is made to

function latest_pheeds($offset = 0) {
            //Confirm if a user is logged before allowing access
            if($this->isLogged()) 
            {
                //Limit
                $limit = 20;
                //user id
                $user_id = $this->session->userdata('user_id'); 
                //load pheeds
                $dt = $this->pheed_model->get_latest_pheeds($limit,$offset);    
                $data = $dt['pheeds']; //data
                $total = $dt['total']; //Total no of rows of data
                $return['pheeds'] = $data;
                echo json_encode($return); //encode in json

            } else {
                $this->output->set_status_header('401',"Attempting Unauthorized Access");
            }
        }

How do I break this data into pages, so I can simply pass the page no as argument to method via the ajax call to implement the load more with jQuery?

Answer 1

Calculate $offset by multiplying (page number - 1) with $limit:

$offset = ($page - 1) * $limit;

So if $page is 1, then it will be (1 - 1) * 20 = 0 * 20 = 0,

if $page is 2, then it will be (2 - 1) * 20 = 1 * 20 = 20

Also rename function parameter $offset to $page

[EDIT]

Also what i would do is to query one row more, than needed, so i can detect if there is next page, eg:

$dt = $this->pheed_model->get_latest_pheeds($limit + 1,$offset);
$next_page = false;
if (count($dt) > $limit) {
    $next_page = true;
    $dt = array_pop($dt); // Excluding the last row so it is same size as $limit
}
// More code....
$return['next_page_exists'] = $next_page;