Question

I’m using PHP and I’m trying to keep an array of the last 10 post id’s in WordPress via $_SESSION array. I know I can add the latest post id like so:

$_SESSION['recently_viewed_posts'][] = $post->ID;

And similarly I could probably follow that command with something like this to remove ones greater than 10:

if( sizeof( $_SESSION['recently_viewed_posts'] ) > 10 )
{
  array_shift( $_SESSION['recently_viewed_posts'] );
}

However this won’t work well if the user reloads the same post a few times, you could end up with something like:

Array
(
    [recently_viewed_posts] => Array
        (
            [0] => 456
            [1] => 456
        )

)

Desired behavior:

• The last 10 post id’s will be keep in an array
• If a visited post is already in the array, it will move to the start or end of the array
• If the size of the array is 10 elements, and a new 11th post is visited, the oldest post id will be removed and the new post id added

I don’t care too much about what side of the array (start or end) the new posts are on, as long as it is consistent. I don’t really care what the array keys are.

What is the best way to accomplish this?

I tried searching for similar questions but didn’t come up with anything useful so I apologize if this is a dupe.

Answer 1

if (!isset($_SESSION['recently_viewed_posts'])) {
    $_SESSION['recently_viewed_posts'] = array();
}
array_unshift($_SESSION['recently_viewed_posts'], $post->ID);
$_SESSION['recently_viewed_posts'] =
    array_slice(array_unique($_SESSION['recently_viewed_posts']), 0, 10);

This pushes new entries onto the beginning of the array, weeds out duplicates using array_unique (which keeps the first occurrence of an item) and limits the array to 10 entries. The most recent post will be at $_SESSION['recently_viewed_posts'][0].