How to get post author name by its ID inside a function?

i’m trying to get the author name using the “the_author_meta” function. After doing that I need to pass the value inside an array and return that with “json_encode”.

Let me show:

$autor_id = $post->post_author;
$autor_name = the_author_meta('user_nicename', $autor_id);
echo $autor_name;

The $autor_name echo works fine but when i do the following code it returns null on my script:

…

$results['author'] = $autor_name;
$posts[] = $results;
}

return json_encode($posts);

it returns that: "author":null

How can i make it display the author name like: "author":admin?