多维数组：删除重复项并将其移至原始数组

Question

I want to remove duplicate arrays, and at the same time add a new key 'duplicates' and the total number of duplicates to the original array. What's the best way to do this using PHP?

Array
(
    [0] => Array
        (
            [w] => 10
            [r] => 10
            [e] => 489
        )

    [1] => Array
        (
            [w] => 10
            [r] => 10
            [e] => 489
        )

    [2] => Array
        (
            [w] => 10
            [r] => 10
            [e] => 489
        )

    [3] => Array
        (
            [w] => 20
            [r] => 20
            [e] => 489
        )

    [4] => Array
        (
            [w] => 10
            [r] => 10
            [e] =>
        )

)

Would become:

Array
(
    [0] => Array
        (
            [w] => 10
            [r] => 10
            [e] => 489
            [duplicates] => 2
        )

    [3] => Array
        (
            [w] => 20
            [r] => 20
            [e] => 489
        )

    [4] => Array
        (
            [w] => 10
            [r] => 10
            [e] =>
        )

)

Answer 1

You can get the unique arrays, and then compare with the original array:

$result = array_map("unserialize", array_unique(array_map("serialize", $input)));
foreach ($result as &$arr) {
    $cnt = 0;
    foreach ($input as $inArr) {
        if ($arr == $inArr) {
            $cnt++;
        }
    }
    if ($cnt > 1) {
        $arr['duplicates'] = $cnt - 1;
    }
}

The result contains what you want.