I've retrieved some data from the database, which is in the following structure:

[0]
  [item_id] = 197
  [dice_chat_css] = "foo"
  [dice_image] = "bar.png"
[1]
  [item_id] = 128
  [dice_chat_css] = "foo"
  [dice_image] = "bar.png"

The most convenient and computationally inexpensive way for me to pass this data to the rest of my (PHP) application is with item_id as the index, because it saves having to loop over the array to look up values. If this was a flat array, I could accomplish this trivially with array_flip, but since it isn't, it's my pick of using either the multidimensional array_flip listed in the comments on PHP.net, or roll my own logic:

for ($i = 0; $i < sizeOf($r); $i++){
    $s[$r[$i]['item_id']]['dice_image'] = $r[$i]['dice_image'];
    $s[$r[$i]['item_id']]['dice_chat_css'] = $r[$i]['dice_chat_css'];
}

I know it's simple, but it feels like I'm reinventing the wheel here. Is there an accepted, more optimized method available or am I being weird about this?