How can I include the user id inside of a shortcode php output?

Question

For the shortcode I am using, the developer of the plugin only added the ability to output content via the shortcode. So the shortcode is all I have to work with.

Here is the default shortcode which does work:

echo do_shortcode("[theplugin_user_data user_id='8']");

With this code, it will output the data for the user with user id of "8". Problem is I can't use this code because if I put that it would give the same data for user id "8" to all comments, while I need it to fetch for each commenter.

So basically I need to fetch the user id of the current comment author, and after fetching their id I need to insert it dynamically into the shortcode.

Here is an idea of what I can come up with but I don't know how to make it work.

echo do_shortcode("[theplugin_user_data user_id='" . phpcodehere . "']");

So how can I get the current commenter's user id and insert it into the shortcode shown above?

---

Note:
I am putting this in the comments section to pull the data. I am using the default wordpress comments system, no plugins or external comments system (the plugin I am pulling data from doesn't have anything to do with comments).

Note 2:
The user ID that is needed is the commenter who MADE the comment, not who is logged in -- please note that this is inside a wordpress comments loop pulling all comments. Here is the comment loop:

function theme_comment( $comment, $args, $depth ) {
    $GLOBALS['comment'] = $comment;

For example, get_comment_author_link() works inside the loop to get the link for the comment author. What I need is the user ID of the comment author.

Note 3:
Not the post author, nor the logged in user; what I need is the comment author user ID.

Answer 1

So I'm assuming the "current commenter" is actually the current user logged into WP. So to get the current user ID, you can simply use get_current_user_id:

echo do_shortcode("[theplugin_user_data user_id='" . get_current_user_id() . "']");

UPDATE

Ok, so we want, then, the comment's author ID:

//$comment = get_comment(); // in your case, it seems you already have a $comment object...
if($comment) {
    if($comment->user_id) echo do_shortcode("[theplugin_user_data user_id='" . $comment->user_id . "']");
    else echo '(no data available)'; // <---- fallback, in case the comment has no known author
}

Hope this helps!