Trying to send a php request via hyperlink to other frame - php

Question

I am a novice to HTML, JavaScript, PHP and pretty much programming in general and I've run into a bit of a problem with a basic shopping cart/e-commerce site I am trying to build.
The main page has a navigation tree in the left frame (before you say "why are you using frames!!!" I know.... My professor for some reason requires us to use outdated techniques in his assignments...). The top right frame contains a product detail which when will show product details when you click on the lowest tier (actual products) of the navbar. When I actually define the product_id in the query I am able to populate the product details table with the correct information. However, when I click on the actual navigation bar links, it doesn't send the product_id to that page for the query.
I'm pretty sure I'm missing something fundamental here, and unfortunately I can't proceed with actually trying to teach myself how to populate the cart until I can get the product details up on the page! Heavy....
Anyway, here is the way I've formatted the links: i.e:
<li>Chocolate Bar
</li>
And here is the php I have on the products page:
<?php
$product_id = $REQUEST['product_id'];
$query_string = "select product_name, unit_quantity, unit_price from products
where (product_id = $product_id)";
$result = mysql_query($query_string,$link);
$num_rows = mysql_num_rows($result);
if ($num_rows > 0 ) {
print "<table border='0'>";
while ($a_row = mysql_fetch_assoc($result) ) {
print "<tr>\n";
print "<td>$a_row[product_name]</td>";
print "<td>$a_row[unit_quantity]</td>";
print "<td>$a_row[unit_price]</td>";
print "</tr>";
}
print "</table>";
}
mysql_close($link)
?>
What am I doing wrong here? I feel like I'm maybe missing some critical PHP on the main page to tell it to send that information over and maybe missing something on the products page to receive it?

Answer 1

Change this
$product_id = $REQUEST['product_id'];
to this
$product_id = $_REQUEST['product_id'];
or this
$product_id = $_GET['product_id'];
You may go through this manual for further information.
Suggestion, unrelated, refrain yourself from using mysql_* functions because they are deprecated and will be discontinued in future.

Answer 2

Try $_GET instead of REQUEST
and try without the ()'s
$query_string = "select product_name, unit_quantity, unit_price from products
where product_id = $product_id";

Answer 3

the issue is in the query, $product_id must be inside another pair of quotes caouse thats the string that gouse to MYsql
$query_string = "select product_name, unit_quantity, unit_price from products
where (product_id = '".product_id."'")";
$result = mysql_query($query_string,$link);

Answer 4

You could indead use REQUEST put you should write it like $_REQUEST. To prevent future errors though you could also use $_GET.
$product_id = $_GET['product_id'];
$query_string = "select product_name, unit_quantity, unit_price from products
where (product_id = '".$product_id."')";