php - sum of values in an array

Question

I need help to sum values in an array. The array is called $results and I need to sum the Total_Sales values for each Month. EDIT - I have the loop below that I need to get the results; however I get notices. How can I improve the code so that I don't get those notices?

Here's the array:

$results

array(4) {
  [0]=>
  array(3) {
    ["Month"]=>
    string(1) "1"
    ["Country"]=>
    string(2) "AU"
    ["Total_Sales"]=>
    string(7) "9095.70"
  }
  [1]=>
  array(3) {
    ["Month"]=>
    string(1) "1"
    ["Country"]=>
    string(2) "CA"
    ["Total_Sales"]=>
    string(9) "113993.00"
  }
  [2]=>
  array(3) {
    ["Month"]=>
    string(1) "2"
    ["Country"]=>
    string(2) "AU"
    ["Total_Sales"]=>
    string(7) "7393.65"
  }
  [4]=>
  array(3) {
    ["Month"]=>
    string(1) "2"
    ["Country"]=>
    string(2) "CA"
    ["Total_Sales"]=>
    string(9) "100279.43"
  }

Here is what I need:

array(2) {
  [1]=>
  array(2) {
    ["MONTH"]=>
    string(1) "1"
    ["Total_Sales"]=>
    float(123088.7)
  }
  [2]=>
  array(2) {
    ["MONTH"]=>
    string(1) "2"
    ["Total_Sales"]=>
    float(107673.08)
  }

I know I need to do a loop but not sure where to go from here.

$newarr=array();
foreach($results as $key) {

}

Edit: This loop gets me the results I need but throws Notices that I don't want.

$newarr=array();
foreach($results as $value) {
    $Month = $value['MONTH'];
    $Total_Sales = $value['Total_Sales'];
    array_key_exists( $Month, $newarr ) ? $newarr[$Month]['MONTH'] = $Month : $newarr[$Month]['MONTH'] = 0;
    array_key_exists( $Month, $newarr ) ? $newarr[$Month]['Total_Sales']+=$Total_Sales : $newarr[$Month]['Total_Sales'] = 0;
}

Notices in the results

Notice: Undefined index: Total_Sales in /var/www/html/analytics/views/sales_year_line_data.php on line 134

Notice: Undefined index: Total_Sales in /var/www/html/analytics/views/sales_year_line_data.php on line 134

Answer 1

inside your loop you just add the values:

$newarr=array();
foreach($results as $val) {
  // index your new array by month so you can easily add to total sales
  $month = $val['Month'];
  $newarr[$month]['Month'] = $month;
  $newarr[$month]['Total_Sales'] += $val['Total_Sales'];
}

// to get rid of your month-based index, use array_values
$finalarray = array_values($newarr);

Answer 2

I gather the keys of the array you need are the month integers (as I can see it starts from 1).

Let's try that:

$totals = array();

foreach ($results as $result) {
    $currentMonth = $result['Month'];
    // For the first record for a given month, we need to add an "empty" record
    if (!array_key_exists($currentMonth, $totals)) {
        $totals[$currentMonth] = array(
            'MONTH' => $currentMonth,
            'Total_Sales' => 0,
        );
    }

    // Then we can sum totals
   $totals[$currentMonth]['Total_Sales'] += $result['Total_Sales'];
}

var_dump($results) gives me:

array (size=2)
  1 => 
    array (size=2)
      'MONTH' => string '1' (length=1)
      'Total_Sales' => float 123088.7
  2 => 
    array (size=2)
      'MONTH' => string '2' (length=1)
      'Total_Sales' => float 107673.08