How do I turn these values from MYSQL into an array

Question

I am working on a custom query to show a few posts. I am able to output all the post ID's. I am trying to turn these ID's into an array so I can use 'post__in' => $myarray in my query. How can I do this?

          <?php
            $allposts = $wpdb->get_results("SELECT `music_id` FROM `custom_table` ORDER BY id DESC LIMIT 5");
              foreach ($allposts as $singlepost) {
                       echo '<p>' .$singlepost->music_id. '</p>';
              }
            ?>

Answer 1

Use $wpdb->get_col. It will return a one-dimensional array that you can use in post__in

$allposts = $wpdb->get_col("SELECT `music_id` FROM `custom_table` ORDER BY id DESC LIMIT 5");

Answer 2

$id = array();
 foreach ($allposts as $singlepost) {
      $id[]= $singlepost->music_id;
}