Query posts only shows 1

OK this is the thing:

I used a query

$args = array(
    'post__in' => array($userPostsInternal),

Taking the fact the following is a string

var_dump($userPostsInternal);
  -> string(13) "128537,128545"

I thought declaring the array here would work

array($userPostsInternal)

But it’s not, therefore thanks to a comment, suggesting me to explode $userPostsInternal converting the string into an array, I then had to remove the array declaration, making the query like:

$args = array(
    'post__in' => $userPostsInternal,