How to merge arrays with same key and different value in PHP?

Question

I have arrays similarly to these:

0 => Array ( [0] => Finance / Shopping / Food, [1] => 47 )            
1 => Array ( [0] => Finance / Shopping / Food, [1] => 25 )                 
2 => Array ( [0] => Finance / Shopping / Electronic, [1] => 190 ) 

I need to create one array with [0] as a key and [1] as value.
The tricky part is that if the [0] is same it add [1] to existing value.

So the result I want is:

array ([Finance / Shopping / Food]=> 72, [Finance / Shopping / Electronic] => 190);

thanks

Solution 1

// array array_merge_values($base[, $merge[, ...]])
// Combines multiple array values based on key
//   (adding them together instead of the native array_merge using append)
//
// $base       - array to start off with
// $merge[...] - additional array(s) to include (and add their values) on to the base
function array_merge_values()
{
  $args = func_get_args();

  $result = $args[0];
  for ($_ = 1; $_ < count($args); $_++)
    foreach ($args[$_] as $key => $value)
    {
      if (array_key_exists($key,$result))
        $result[$key] += $value;
      else
        $result[$key] = $value;
    }
  return $result;
}

$array1 = Array('foo' => 5, 'bar' => 10, 'foobar' => 15);
$array2 = Array('foo' => 20,                             'foohbah' => 25);
$array3 = Array(            'bar' => 30);
var_dump(array_merge_values($array1,$array2,$array3));

Result:

array(4) {
  ["foo"]=>
  int(25)
  ["bar"]=>
  int(40)
  ["foobar"]=>
  int(15)
  ["foohbah"]=>
  int(25)
} 

That what you're looking for?

Solution 2

This should work:

$outArray = array()
foreach($superArray as $subArray) {
  if(array_key_exists($outArray,$subArray[0])) { 
    $outArray[$subArray[0]] += $subArray[1]; 
  } else { 
    $outArray[$subArray[0]] = $subArray[1]; 
  }
}

Comments

[dqhendricks]

it looks as though you should be using key/value pairs instead of two array elements, one being a key, and a second being a value. is there a reason you can't build the array in the first place like this? Array('Finance / Shopping / Food' => 47, 'Finance / Shopping / Food' => 25, 'Finance / Shopping / Electronic' => 190) This would make the rest of what you are trying to do far more simple.

[dqhendricks]

I'm not even entirely sure your syntax works as is. array keys can either be strings or numeric values, but yours appear to be constants divided by each other and other weird stuff. you may want to read up on php arrays here: php.net/manual/en/language.types.array.php

[fredley]

In fact, it'll probably work without the if/else, just loop over the whole thing with $outArray[$subArray[0]] += $subArray[1].

[Brad Christie]

It will work, but not a good idea to perform a += on an uninitialized value (although I suppose in this case it's trivial, assuming 0 is the "base" value.)

[fredley]

@Brad My thoughts exactly. My answer is more correct, but PHP is suitably flexible/dirty to allow the code in the comment :-)