Q:

MySQL / PHP - How to match an author id to a user id and display username

another question. I need to display a username and so what I'm doing is getting the author id (which is '1'), and then using a query saying get the username from the users table where the author id is the same as the user id.
My problem is that I'm getting the value of '1' returned as I've said above and the following is my code. Am I missing something here or...?
 $users = mysqli_query($sql, "SELECT * FROM users WHERE userid = '$authorid'") or die($users . "<br/>" . mysqli_error($sql));

 while($userData = mysqli_fetch_array($users)) {
    $postAuthor = $usersData['username'];
} 

Edit 1
I said also mention the above information should show the name 'Dan'.
The user 'Dan' has a user id of 1 should the author id should be 1 (which it is) from the post row. This is the only use of anything to do with the user table so it's not being overridden anywhere. I'm so confused.

A:

This should have been an error:
while($userData = mysqli_fetch_array($users)) {
       ^^ no s
    $postAuthor = $usersData['username'];
                    ^^ used different variable name
}

Note: Use prepared statements also in this case, you're using mysqli anyways.
$select = $sql->prepare("SELECT * FROM users WHERE userid = ?");
$select->bind_param('i', $author_id);
$select->execute();
$results = $select->get_result();

while($userData = $results->fetch_assoc()) {
    $postAuthor = $userData['username'];
}

