How to get unique value in multidimensional array

Question

I have done a lot of looking around on the overflow, and on google, but none of the results works for my specific case.

I have a placeholder array called $holder, va

Answer 1

Seems pretty simple: extract all pid values into their own array, run it through array_unique:

$uniquePids = array_unique(array_map(function ($i) { return $i['pid']; }, $holder));

The same thing in longhand:

$pids = array();
foreach ($holder as $h) {
    $pids[] = $h['pid'];
}
$uniquePids = array_unique($pids);