从数组中删除双重条目

Question

I have the following array in php:

[0] => Array(
  (
    [post_id] => 492,
    [user_id] => 1
  )
[1] => Array(
  (
    [post_id] => 501,
    [user_id] => 1
  )
[2] => Array(
  (
    [post_id] => 568,
    [user_id] => 13
  )
[3] => Array(
  (
    [post_id] => 897,
    [user_id] => 13
  )

What I want to do, is to delete the ones where the user_id already exists. So the result should look like this:

[0] => Array(
  (
    [post_id] => 492,
    [user_id] => 1
  )
[1] => Array(
  (
    [post_id] => 568,
    [user_id] => 13
  )

I need an array, in which every user_id only exists one time.

array_unique() doesn't work for this example. Any ideas?

Thanks!

Answer 1

You can loop through and find unique values as you go:

$exists = array();
foreach($items as $key => $item) {
    if(!in_array($item['user_id'], $exists)) {
        $exists[] = $item['user_id'];
    } else {
        unset($items[$key]);
    }
}

This will unset any arrays that already exist in the $exists array.