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As you can see in Figure 5-2, the URL doesn’t include any affiliate IDs any more, yet the page retained

the affiliate ID. And you achieved this with only a few lines of PHP code! Everything starts, again, with

a mod_rewrite rule:

RewriteRule ^Products/.*-C([0-9]+)/.*-P([0-9]+)\.html$

i

/product.php?category_id=$1&product_id=$2

&%{QUERY_STRING}

[L]

The

{QUERY_STRING}

bit is a special variable provided by mod_rewrite that represents the query string in

the URL. The

RewriteRule

would still match for keyword-rich URLs that contain query string parameters

(such as

http://seophp.example.com/Products/SEO-Toolbox-C6/Link-Juice-P31.html?aff_

id=987

), but this time you append those parameters to the rewritten URL.

This way, when

product.php

is executed, it’ll have access to the

aff_id

parameter. The only code you’ve

added to

product.php

is minimal, and it consists of verifying if the

aff_id

parameter exists in the query

string. In case it does, you save the affiliate ID value in the user session:

// start PHP session

session_start();

// save affiliate ID

if (isset($_REQUEST[‘aff_id’]))

{

$_SESSION[‘aff_id’] = $_REQUEST[‘aff_id’];

}

The redirection itself is done by our old friend, the

fix_category_product_url()

function. This function

verifies if the URL is identical to a clean product URL, and in case it’s not, it does an automatic 301 redirect

to the “proper” URL; in this case, that proper URL will be a product URL that doesn’t contain the

aff_id

parameter.

// redirect requests proper keyword-rich URLs when not already there

fix_category_product_url();

The first time a product page is loaded with an affiliate ID, it will be redirected to its proper version that

doesn’t contain any query string parameters. When

product.php

reloads, it will reach the code that dis-

plays the product details, and the affiliate ID. This time, the affiliate ID is read from the session:

// display affiliate details

echo ‘<br /><br /> You got here through affiliate: ‘;

if (!isset($_SESSION[‘aff_id’]))

{

echo ‘(no affiliate)‘;

}

else

{

echo $_SESSION[‘aff_id’];

}

Example #2

The second technique involves dynamic URLs. When working with dynamic URLs, the solution is slightly

different. In this case you don’t need to deal with mod_rewrite anymore, but you need a way to read and

remove the affiliate IDs from a dynamic URL, and then redirect to this version of the URL.

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Chapter 5: Duplicate Content

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