Cannot extract columns from array using pluck

I’m trying to extract the id value from a list of associative array, this is the value of $request->post('files'):

array:2 [
  0 => array:2 [
    "id" => "21"
    "name" => "aviary-image-1429352137570.jpeg"
  ]
  1 => array:2 [
    "id" => "22"
    "name" => "1.jpg"
  ]
]

I tried:

$fileList = $request->post('files');
dd($fileList->pluck('id'));

But this returns:

Expected type ‘object’. Found ‘string|array|null’

So for the moment to fix this I have created a loop which iterates over the array and get only the id.

The expected result is: [21, 22]

Is there any way to do this without loop?