Online PHP editor | refs for OgUSj

<?php $arr = [ 'itemA' => [ 'product_id' => 1, 'category_id' => 1, ], 'itemB' => [ 'product_id' => 2, 'category_id' => 2, ], 'itemC' => [ 'product_id' => 3, 'category_id' => 1, ], 'itemE' => [ 'product_id' => 4, 'category_id' => 1, ], 'itemD' => [ 'product_id' => 5, 'category_id' => 2, ], ]; uasort($arr, function ($a, $b) { if ($a['category_id'] == $b['category_id']) { return $a['product_id'] - $b['product_id']; } return $a['category_id'] < $b['category_id'] ? -1 : 1; }); var_dump($arr);