如何按類別轉換數組和排序元素？

Question

請幫忙。

無法理解如何按數組中的類別對項目進行排序。

我有帶產品的普通數組：

Item 1 (Category C)
Item 2 (Category B)
Item 3 (Category A)
Item 4 (Category C)
Item 5 (Category B)
Item 6 (Category A)

並希望按類別對列表進行排序，例如：

Category A
  Item 3
  Item 6

Category B
  Item 2
  Item 5

Category C
  Item 1
  Item 4

原始數組是這樣的：

array(4) {
  [0]=>
  array(19) {
    ["product_name"]=> "Samsung GALAXY Note 3"
    ["categories_id"]=> "3"
    ["categories_name"]=> "Smartphones"
  }
  [1]=>
  array(19) {
    ["product_nam"]=> "Samsung GALAXY Note 8"
    ["categories_id"]=> "2"
    ["categories_name"]=> "Tablets"
  }
  [2]=>
  array(19) {
    ["product_nam"]=> "Samsung GALAXY Tab 3"
    ["categories_id"]=> "3"
    ["categories_name"]=> "Smartphones"
  }
  [3]=>
  array(19) {
    ["product_name"]=> "Samsung ATIV Smart PC"
    ["categories_id"]=> "1"
    ["categories_name"]=> "Laptops"
  }
}

Answer 1

嘗試：

foreach($array as $value){
    $newArray[$value["categories_name"]][] = $value;
}
print_r($newArray);

Answer 2

// First group items by categories
$groupedData = [];
foreach ($originalArray as $item) {
    $categoryID = $item['categories_id'];
    if (!isset($groupedData[$categoryID])) {
        $groupedData[$categoryID] = [
            'name' => $item['categories_name'],
            'items' => [],
        ];
    }
    $groupedData[$categoryID]['items'][] = $item['product_name'];
}

// Next you can sort $groupedData with sorting functions

// Then output data
foreach ($groupedData as $array) {
    echo $array['name'] . ':<br />';
    foreach ($array['items'] as $item) {
        echo $item . '<br />';
    }
}

Answer 3

試試這個功能：

/**
 * Creates custom array map from 2-dimensional $arr with predefined structure, changing its keys by value, which is present in second dimension.
 * 
 * @param array $arr 2-dimensional array, which should be mapped, basing on subarray value
 * @param string $targetKey Subarray key name. Value, which corresponds to this key, will be set as key in 1st dimension, and this 1st-dimensional key will correspond to subarray
 * @param boolean $add If TRUE, every res. arr val represented as indexed list of subarrays. Otherwise every res. arr val contains one sub. arr 
 * @return array Mapped arr | original arr, if $targetKey wasn't found in any subarray
 */
public static function setKeyFromVal($arr, $targetKey, $add = false)
{
    $mappedArr = [];

    foreach ($arr as $subArr) {

        if (array_key_exists($targetKey, $subArr)) {

            if ($add) {
                $mappedArr[$subArr[$targetKey]][] = $subArr;
            } else {
                $mappedArr[$subArr[$targetKey]] = $subArr;
            }

            unset($mappedArr[$subArr[$targetKey]][$targetKey]);
        }
    }
    return empty($mappedArr) ? $arr : $mappedArr;
}

調用它（用true論據！ ）：

setKeyFromVal($a, 'categories_id', true);

categories_id是排序鍵，您可以更改它。