How to put a lot of information in the class?
Please provide some more information, like the example contents of $infos. It is hard to find any other solution if we are not able to understand your current solution in the first place.

However, there already are some issues with your code:


avoid using variable names like $i and $k. They should be named according to their meaning (see example for $k)
$i seems not to be read in your code
$k and all arrays seem to be used uninitialized


Your while loop seems a bit too clever to me. All you want to do is iterate $k so you should instead use a for loop:

for($childIndex = 0; $size = $sizes_info-&gt;children($childIndex); ++$childIndex)
    $sizes_arr[] = $size-&gt;plaintext;


The foreach loops look as if they could be better implemented by array_map:

$item_infos = $infos-&gt;find('.products-list-item product-label, .products-list-item .products-list-item__brand, .products-list-item .products-list-item__type,.products-list-item .price');
$get_plaintext = function($item_info) { return $item_info-&gt;plaintext; };
$item_info_arr = array_map($get_plaintext, $item_infos); 


A foreach loop could be as readable however then you should at least use named variables (like $item_infos but with better names (I have no idea what this find returns)) to keep the head of the loop short and readable.