您不需要使用任何复杂的序列化或编码来创建组合键以进行分组。只需将每行的值内爆（假设它们都包含相同顺序的相同列）以创建结果数组的标识键。
在第一次遇到时，将行的数据存储在组中，并将组的计数设置为1;在任何后续遭遇中，增加该组的计数器。
代码：（Demo）

$result = [];
foreach ($array as $row) {
    $compositeKey = implode('_', $row);
    if (!isset($result[$compositeKey])) {
        $result[$compositeKey] = $row + ['count' => 1];
    } else {
        ++$result[$compositeKey]['count'];
    }
}
var_export(array_values($result));

输出：

array (
  0 => 
  array (
    'manufacturer' => 'KInd',
    'brand' => 'ABC',
    'used' => 'true',
    'count' => 2,
  ),
  1 => 
  array (
    'manufacturer' => 'KInd',
    'brand' => 'ABC',
    'used' => 'false',
    'count' => 1,
  ),
)

其他利用多个标识列值进行分组的帖子：

• Group/Merge rows from two 2d arrays based on 3 identifying columns and fill missing column values with null
• Group rows of data, sum number of occurrences in each group, and print data as formatted strings
• Group data in a multidimensional array based on two columns
• Group rows of a multidimensional array and form comma-separated values within each group
• Group rows by two columns, filter grouped data to only keep the lowest value, and restructure associative rows
• Group rows of data, maintain a subarray of ids within the group, and only present the lowest id in each group as the first level key
• Group multidimensional array data based on two column values and sum values of one column in each group
• how to create a pivot array in php

如果我没理解错的话，这个应该会有帮助

function getUniqWithCounts(array $data): array
{
    $result = [];
    foreach ($data as $item) {
        $hash = md5(serialize($item));

        if (isset($result[$hash])) {
            $result[$hash]['count']++;
            continue;
        }
        $item['count'] = 1;
        $result[$hash] = $item;
    }

    return array_values($result);
}