Hello @bumbar

I think is the solution you want have.

$orders = collect([
    ['id' => 33, 'OrderNumber' => 505, 'user_id' => 55],
    ['id' => 22, 'OrderNumber' => 505, 'user_id' => 152],
    ['id' => 20, 'OrderNumber' => 505, 'user_id' => 130],

    ['id' => 96, 'OrderNumber' => 494, 'user_id' => 209],
    ['id' => 95, 'OrderNumber' => 494, 'user_id' => 67],

    ['id' => 91, 'OrderNumber' => 492, 'user_id' => 234],
    ['id' => 86, 'OrderNumber' => 492, 'user_id' => 195],
]);

$results = $orders->groupBy(['OrderNumber'])
    ->map(static function(Collection $group): Collection {
        return $group->skip(1);
    })->flatten(1)
;
$results->dump();

Ps. I have updated your post to get the code blocks more readable.