Passing Form Var's to SQL Statement then Into DB

[gregor002]

I'm in the process of building a bookstore where customers can add Book Reviews. The sku# of a product is passed to a page level var called $sku via $_GET. I have a form that lets customers add reviews of a product. This is what it looks like:

<form name="review_form" action="review_added.php" method="post">

<input type="hidden" value="<?=$sku ?>" name="prod_sku">

<p>
<label for="first">Firstname</label><br />
<input type="text" value="<? $firstname ?>" id="firstname" name="firstname" maxlength="30" onfocus="this.style.background='#fff';" onblur="this.style.background='#eee';" class="text" /></p>

<p>
<label for="last">Lastname</label><br />
<input type="text" value="<? $lastname ?>" id="lastname" name="lastname" maxlength="50" onfocus="this.style.background='#fff';" onblur="this.style.background='#eee';" class="text" /></p>

<p>
<label for="title">Review Title</label><br />
<input type="text" value="<? $review_title ?>" id="review_title" name="review_title" size="60" maxlength="100" onfocus="this.style.background='#fff';" onblur="this.style.background='#eee';" class="text" />
</p>

<p>
<label for="review">Your Review</label><br />
<textarea cols="40" rows="15" id="review" name="review" onfocus="this.style.background='#fff';" onblur="this.style.background='#eee';"></textarea>
</p>
<input type="submit" value="Add Review" />
</form>

Here is the process page of this form:

//review_added.php


db_connect();
$reviews_table = "greg_php_reviews";

/* insert into table */
$sql = "INSERT INTO $reviews_table
(id, firstname, lastname, reviewDate, title, review, sku)
VALUES
('', '$firstname','$lastname', NOW(), '$review_title', '$review', 'prod_sku')";

/*get results */

$query = mysql_query($sql) or die(mysql_error());

?> 

My problem is filling the sku field in the table. I am writing the value of $sku in the form as a hidden value and I would like this to be put into the database. Say that $sku for a specific product is 888888. How do I get 88888 into the db sku field?

Thanks!