I have an array called $results that I need to sum the Total_Sales per Month. I have the code below that gives me the results I need but I also get notices. How do I improve the code?
$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's my code so far. The array that it returns are the results that I need but I get notices
Code
$newarr=array();
foreach($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;
}
$newarr
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)
  }
Notices
Notice: Undefined index: Total_Sales in /var/www/html/analytics/views/sales_year_line_data.php on line 120
Notice: Undefined index: Total_Sales in /var/www/html/analytics/views/sales_year_line_data.php on line 120
 
    