Group rows in a 2d array and count number of rows in each respective group

Question

I have an array of 200 items. I would like to output the array but group the items with a common value. Similar to SQL's GROUP BY method. This should be relatively easy to do but I also need a count for the group items.

Does anyone have an efficient way of doing this? This will happen on every page load so I need it to be fast and scalable.

Could I perhaps dump the results into something like Lucene or SQLite then run a query on that document on each page load?

Answer 1

Just iterate over the array and use another array for the groups. It should be fast enough and is probably faster than the overhead involved when using sqlite or similar.

$groups = array();
foreach ($data as $item) {
    $key = $item['key_to_group'];
    if (!isset($groups[$key])) {
        $groups[$key] = array(
            'items' => array($item),
            'count' => 1,
        );
    } else {
        $groups[$key]['items'][] = $item;
        $groups[$key]['count'] += 1;
    }
}