在数组中查找重复值，该数组创建一个新数组，其中键为重复键，值为dupe

Question

I am trying to find all duplicates in my array, and create a new array which has keys as the duplicate values key and value as the key of its duplicate

example

[1] => 10
[2] => 11
[3] => 12
[4] => 12
[5] => 12
[6] => 13
[7] => 13

After I apply the duplicate check I just need

[4] => [3] // value of key 4 is dupe of key 3
[5] => [3] // value of key 5 is dupe of key 3
[7] => [6] // value of key 7 is dupe of key 6

this gets me all duplicate keys, but I need duplicate keys with values as the keys which are duplicate

$arr_duplicates = array_keys(array_unique( array_diff_assoc( $array, array_unique( $array ) ) ));

Thanks

Answer 1

Try this for potential speed boost over the other solution. Will however use a lot more memory on large data sets.

<?php

$orig = array(
    1   => 10,
    2   => 11,
    3   => 12,
    4   => 12,
    5   => 12,
    6   => 13,
    7   => 13
);

$seen  = array();
$dupes = array();

foreach ($orig as $k => $v) {
    if (isset($seen[$v])) {
        $dupes[$k] = $seen[$v];
    } else {
        $seen[$v] = $k;
    }
}
unset($seen);

var_dump($dupes);