Online PHP editor | output for b3KAi

<?php $array = [ ['_id' => '5f76b1788ee23077dccd1a2c', 'product' => ['_id'=>'5d0391a4a72ffe76b8fcc610'], 'count'=> 1], ['_id' => '5f76b6288ee2300700cd1a3a', 'product' => ['_id'=>'5d0391b6a72ffe76b8fcc611'], 'count'=> 1], ['_id' => '5f76d2488ee23083d3cd1a4a', 'product' => ['_id'=>'5d0391b6a72ffe76b8fcc611'], 'count'=> 1] ]; $productCounts = []; foreach ($array as $item) { $productId = $item['product']['_id']; $productCounts[$productId] = ($productCounts[$productId] ?? 0) + $item['count']; } var_export($productCounts);