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$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");
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1 Answer 1

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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

See also: array_reduce() arsort()

Update

You will see some crazy results when you look at this code in different versions of PHP.

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8 Comments

Jack, Thanks "Parse error: syntax error, unexpected T_FUNCTION" $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), ); $grouped = array_reduce($inventory, function(&$result, $item) { @$result[$item['fruit']] += $item['price']; return $result; }, array());
@CanadaPHP Updated the answer to work with older versions of php.
@CanadaPHP What do you mean without you rewriting? Rewrite what exactly?
your updated code generated an error Warning: arsort() expects parameter 1 to be array, integer
@CanadaPHP I don't know what you mean, it runs fine here.
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