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Except for the new

R

option at the end, there’s nothing new for you here — but that option represents

an important difference! With or without the

R

option, the visitor would end up transparently seeing

the content provided by

bar.php

. However, when redirection is used, the user’s web client actually

makes two calls to the web server. First it asks for

foo.php

; as a response, it gets a 301 redirect code in

the HTTP header, indicating

bar.php

as the new location. Then the web client requests

bar.php

, and

informs the user that a new URL has been loaded by updating the URL displayed in the address bar.

In PHP, you redirect by adding HTTP headers using the

header()

function. If you want

foo.php

to do

a 301 redirect to

bar.php

, your

foo.php

should look like this:

<?php

header(‘HTTP/1.1 301 Moved Permanently’);

header(‘Location: http://www.example.com/bar.php’);

?>

In practice, when a site redesign involves changing URLs, the webmaster should at least 301 redirect the

most important URLs to their new counterparts. Otherwise link equity will be lost.

Using a series of 301 redirects mitigates this problem. If your site is already indexed by search engines,

you need to systematically rewrite old URLs to new URLs.

Using Redirects to Change File Names

In the exercise that follows you update the product pages you created in Chapter 3 to redirect all

the dynamic URLs to their keyword-rich versions. Currently, the same content can be retrieved using

both dynamic URLs and keyword-rich URLs (see Figure 3-9 and Figure 3-12 from Chapter 3); the follow-

ing two links would get to the same content:

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

and

http://seophp.example.com/product.php?category_id=6&product_id=31

To avoid any problems that can result from two links generating this duplicate content, make sure that

the visitor is always redirected to the proper keyword-rich URL, if a different URL was used. This is crit-

ical during a migration to such URLs on a preexisting web site, because the old URLs will be definitely

indexed.

Alright, we’re sure you’re eager to write some code!

When just the

Location

header is mentioned without explicitly mentioning the

status code, a 302 temporary redirect is implied. Keep this in mind.

85

Chapter 4: Content Relocation and HTTP Status Codes

c04.qxd:c04 10:40 85

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