Online PHP editor | refs for mVaBB

<?php $rows = [ ['3', '2022-01-03'], ['5,3', '2022-01-15'], ['4', '2022-01-27'], ['5', '2022-02-01'], ['7', '2022-02-09'], ['3,2', '2022-01-16'], ]; $counts = []; foreach($rows as $row){ $ids = explode(',', $row[0]); $month = date('m', strtotime($row[1])); foreach($ids as $id){ if(!array_key_exists($id, $counts)){ $counts[$id] = []; } if(!array_key_exists($month, $counts[$id])){ $counts[$id][$month] = 0; } $counts[$id][$month]++; } } var_dump($counts);