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Disabling URL-Based Session Handling for Spiders

As discussed in Chapter 5, PHP’s trans_sid feature, which performs automatic modification of URLs

and forms to include session variables, is used to preserve session state for those users who do not

accept cookies. However, this has the side effect of sending spiders a potentially infinite amount of

duplicate content. For this reason, nowadays many web sites turn this feature off altogether.

However, because this feature can be turned on and off dynamically in PHP code, cloaking can be employed

to dynamically turn it on and off based on whether the visitor is a human or a search engine spider. This

allows the site to both accommodate users, but not confuse a spider when it visits with an infinite number

of semantically meaningless URL-variations containing different session IDs. Using the cloaking toolkit in

this chapter, it would be implemented as follows:

This code should be placed at the top of a PHP script, and before any headers or output is sent to the client.

if (SimpleCloak::isSpider())

{

ini_set (‘session.use_trans_sid’, 0);

}

else

{

ini_set (‘session.use_trans_sid’, 1);

}

session_start();

Obviously, your site must also not require a session to be functional either — because search engines will

not accept cookies regardless.

Other Cloaking Implementations

The preceding implementation of cloaking works if you have the source code to your application and you

are willing and able to modify it. If not, there are cloaking toolkits that allow you to easily and dynami-

cally serve different content to various user agents. One such toolkit is KloakIt from Volatile Graphix, Inc.

You can find it at

http://www.kloakit.com

. It is written by and utilizes the same cloaking data used as

provided by Dan Kramer.

Implementing Geo-Targeting

Geo-targeting isn’t very different than cloaking — so you’ll probably feel a little deja vu as you read this

section. After creating the database table

geo_target_data

, you’ll create a class named

SimpleGeoTarget

that includes the necessary geo-targeting features.

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Chapter 11: Cloaking, Geo-Targeting, and IP Delivery

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