Widget : html 2 dimensional array doesn’t work

Ok, with a quick dirty hack I have achieve my goal :

Instead of myCollection[id][myField] I give to the get_field_name‘s function something like this : collection][id][field.

So the generated code became :

name="widget-pricetable-ibsciss-widget[2][box][1]Widget : html 2 dimensional array doesn't work"

And my array just look perfect now :

array(3) { 
  ["title"]=> string(12) "Global title" 
  ["box"]=> array(2) { 
    [0]=> array(2) { 
      ["title"]=> string(6) "title1" 
      ["price"]=> string(6) "price1" 
    } 
    [1]=> array(2) { 
      ["title"]=> string(6) "title2" 
      ["price"]=> string(6) "price2" 
    } 
  } 
  ["box_title"]=> string(9) "Box title" 
} 

PS : only for information purpose this is the get_field_name method from WordPress :

function get_field_name($field_name) {
    return 'widget-' . $this->id_base . '[' . $this->number . '][' . $field_name . ']';
}