Problem sending variables

[melissal]

So I'm trying to build a basic shopping cart product page, wherein the the user can select put a date into a form and that date gets passed into the URL after which it gets put into the session for the specific cart item. The trouble that I'm having is putting it into the URL in the first place along with the other variables that I need.

 

Here's my code...I know I'm doing something wrong but I'm not sure how to fix it...

 

<form action="reserve.php" method="get">
Date Requested: <input name="reservation_date" id="reservation_date" type="text" value="dd/mm/yy">
</form>
<?php 
echo "<center>
<a href='reserve.php?reservation_date=".$_GET['reservation_date']."&category_id=$category_id&product_id=".$_GET['product_id']."'>
<img src='images/reserve_button.gif' border='0'></a></center>

[Ken2k7]

Well for starters, you need to put a submit button in the form so you can retrieve the information.