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<?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);
Output for 7.1.25, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
array(5) { ["itemA"]=> array(2) { ["product_id"]=> int(1) ["category_id"]=> int(1) } ["itemC"]=> array(2) { ["product_id"]=> int(3) ["category_id"]=> int(1) } ["itemE"]=> array(2) { ["product_id"]=> int(4) ["category_id"]=> int(1) } ["itemB"]=> array(2) { ["product_id"]=> int(2) ["category_id"]=> int(2) } ["itemD"]=> array(2) { ["product_id"]=> int(5) ["category_id"]=> int(2) } }

preferences:
117.22 ms | 1503 KiB | 4 Q