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<?php $months = [ '2023-04', '2023-03', '2023-04', '2023-04', '2023-02', ]; $amounts = [ 833, 223, 829, 220, 498 ]; $sums = []; foreach($months as $i => $month) { if (!isset($sums[$month])) { $sums[$month] = 0; } $sums[$month] += $amounts[$i]; } var_dump($sums);

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