Insert query not working

I am trying to insert information into my mysql database using the following code:

//$query = "INSERT INTO book_sales (wborder_number) VALUES ($order_number)"; // this works

$query = "INSERT INTO book_sales (wborder_number, wbstate) VALUES ($order_number, $state)"; // error in syntax

mysqli_query($cnct, $query);

(I attempted to format that using Control-K, but it doesn’t look like it worked. Sorry!)

If I use the first query, it inserts the order_number just fine. If I use the second query, though, I get the following error:

It seems to be trying to insert into a field labeled “Alabama” in my database, which contains no such field. The field I am trying to insert into is called, as in my code, “wbstate”, which is a valid field, as shown in the following clip from my phpMyAdmin:

The value contained in the variable “$state”, though, is indeed “Alabama”, so it seems to be confusing the value in the variable with the name of the field!

I have tried many different combinations of inserting into various fields, and they all seem to do the same. If I only insert into the “order_number” field, it works fine, but if I try to insert into any other field, I get an error message similar to the one displayed. Sometimes it will state a field which is different than what I call for; other times I just get an error saying that there is an error in my syntax. It just seems to me to be “screwy”!!! Does anyone know what is going on here?