多维数组求和和排序

$inventory = array(

   array("fruit"=>"orange", "price"=>3),
   array("fruit"=>"kiwi", "price"=>2),
   array("fruit"=>"apple", "price"=>3),
   array("fruit"=>"apple", "price"=>3),
   array("fruit"=>"apple", "price"=>3),
   array("fruit"=>"orange", "price"=>3),
   array("fruit"=>"banana", "price"=>10),
   array("fruit"=>"banana", "price"=>10),

);

// what I wish to do is loop through this array and add all of the 'prices' for each // unique key 'fruit' and then sort them afterwards

// ex. the output I wish to achieve would be an array as such:

$sum_array = array("banana"=>"20", "apple"=>"9", "orange"=>"6", "kiwi"=>"2");

Well, just group them by fruit and then sort the end-result:

function groupFruits(&$result, $item) 
{
    $key = $item['fruit'];
    @$result[$key] += $item['price'];

    return $result;
}

$grouped = array_reduce($inventory, 'groupFruits', array());

arsort($grouped);

print_r($grouped);

Demo