Use results from one array in another array - arrays

Question

I have a logged in user following other users in a blog. I would like my logged in users to see posts from users they follow.
I run a query that returns a list of user_ids (user_id1) a logged in user (user_id2) follows in an array. I then run the array through a foreach loop to get the list of users as user ids and place it in a new array. The returned user1_ids are echoed as a string. I would now like to use the returned user1_ids in another array that only displays posts based on the user1_ids.
The issue is that the values are returned as a string and my second array used in the posts only reads the first number of the first array as the values are returned as a string and not integers.
How can I use the results from my first array in my second array 'author__in'=> array()? Do I need to convert the string into integers or is there a better method?
// The database query that returns the array
<?php
$currentloggedinuser = get_current_user_id();
$followers_query = $wpdb->get_results("SELECT ID, user_id1 FROM wp_followers WHERE user_id2 = '$currentloggedinuser' ") ?>
// the returned array from the query through foreach placed in another array
<?php
$following_id = array();
foreach ($followers_query as $follower) {
$following_id[] = $follower->user_id1;
sort($following_id);
$following_ids = implode(", ",$following_id);
}
?>
// the resulting number values returned as a string
<?php echo $following_ids; ?>
<?php
$args = array(
'author__in'=> array($following_ids), // user1_ids I'd like to include from the array above
'post_type' => 'post'
);

Answer 1

This would probably work. I did not test it but it should be fine.
Here is some info on the $wpdb::get_col method
<?php
$currentloggedinuser = get_current_user_id();
// Get an array containing only the user_id1 values.
// It's a good habit to use the prepare method of $wpdb
// for security and ease of reading the code
// Also, you should use $wpdb->prefix instead of using the 'wp_' for the table name
// that prefix can be changed and your code would break.
$followers = $wpdb->get_col(
$wpdb->prepare(
"SELECT user_id1 FROM {$wpdb->prefix}followers WHERE user_id2 = %d",
$currentloggedinuser
)
);
sort($followers); // or you can just apply sorting in the query above
// Directly echo the imploded array.
// No need to store it in a variable to do so unless you want to use it somewhere else
echo implode(', ', $followers);
$args = array(
'author__in'=> $followers, //use the array we got from the query
'post_type' => 'post'
);