如何在php中提取数组键和值以获得新数组？

我有一个关联数组，其中包含关键字category_id和item_code及其各自的值，如下所示

$arr = Array
(
 [0] => Array
    (
        [category_id] => 1
        [item_code] => RED 
    )
[1] => Array
    (
        [category_id] => 1
        [item_code] => GREEN
    )
[2] => Array
    (            
        [category_id] => 2
        [item_code] => BLUE
    )
[3] => Array
    (
        [category_id] => 3
        [item_code] => YELLOW
    )
[4] => Array
    (
        [category_id] => 3
        [item_code] => WHITE
    )
[5] => Array
    (
        [category_id] => 3
        [item_code] => BLACK
    )
);

现在我想提取这个数组，得到像这样的新数组

$new_arr = Array
 (
 [0] => Array
    (
        [0] => RED
        [1] => GREEN
    )
[1] => Array
    (
        [0] => BLUE
    )
[2] => Array
    (
        [0] => YELLOW
        [1] => WHITE
        [2] => BLACK
    )   
);

如何获取此新阵列？如果你有什么想法，请给我一些建议。谢谢

给你：

foreach($arr as $v) {
  $new_arr[$v['category_id']][] = $v['item_code'];
}
$new_arr = array_values($new_arr);

---

您的代码在哪里？您的是post json字符串数组吗？第一个数组总是按类别ID排序吗？这样就不会有$new_arr[0]，对吗？因为没有0的类别\u id。