array array_sum get error message

Results from the table:

Code:

Array (
   [0] => stdClass Object (
       [ID] => 00058
       [income_campaign] => 00001
       [income_country] =>
       [income_value] => 0.00
       [income_date] => 2019-02-11
       )
   [1] => stdClass Object (
       [ID] => 00056
       [income_campaign] => 00001
       [income_country] => 1US, 3PH, 2CN, 9TH
       [income_value] => 12.00
       [income_date] => 2019-02-12
   )
   [2] => stdClass Object (
       [ID] => 00059
       [income_campaign] => 00001
       [income_country] => 1US
       [income_value] => 12.00
       [income_date] => 2019-02-10
   )
   [3] => stdClass Object (
       [ID] => 00061
       [income_campaign] => 00001
       [income_country] => 2US
       [income_value] => 12.00
       [income_date] => 2019-02-09
   )
)

I want to sum an income_value value, so the results obtained are 36.00

I have tried this code but always get an error message:

PHP Code:

$sum = array();

foreach ($data['data_user_income'] as $a => $b) {

   foreach ($b as $c => $d) {
      $sum[$c]+=$d;
   }
}
print_r($sum);

// Error message :
// Message: Undefined index: ID,income_value .... etc.