Eric Nagel

There’s been talk lately that the Google Panda loves keyword-rich subdomains, so I decided to test this on my coupon website.

Aside from a WordPress blog, the pages on the coupon website are all driven from a coupon database. I use a system I wrote myself, although you can just as easily use a service like For Me to Coupon.

The merchant pages on the site look like this:
clubcouponcode.com/Flirty-Aprons-m925.php

The “m925” part in the filename tells my system this is merchant 925 in the database. If you change that ID, you’ll be shown another merchant’s coupons instead (and the URL will be corrected).

Previously, the full URL was www.clubcouponcode.com/Flirty-Aprons-m925.php, but I wanted to feed the Google Panda by putting the merchant name in the subdomain. Of course, adding all of those DNS entries wasn’t an option, and adding all of those ServerAliases in apache wasn’t an option, either. After all, there are nearly 3,000 merchants in the database. So to get over this hurdle, I’m using wildcard DNS.

The first step is to add an A-record to your zone file, such as:

A	*	184.72.255.56

Of course, you want to point this to your server, not mine.

Then, you need to add the ServerAlias to the apache configuration. I’m using Plesk, so I create a vhost.conf file in /var/www/vhosts/clubcouponcode.com/conf which contains:

ServerAlias *.clubcouponcode.com

Now, you can go to anysubdomainyouwant.clubcouponcode.com and the site will come up.

The next step is to automatically redirect the pages to their new, keyword-friendly subdomain URLs. Here’s how I’m checking to make sure the user is on the right page, and redirecting if not:

$cURIActual = 'http://' . $_SERVER['SERVER_NAME'] . $_SERVER['REDIRECT_URL'];
$cURIExpected = 'http://' . strtolower(simplify($rsMerchantData['cName'], true)) . '.clubcouponcode.com/' . simplify($rsMerchantData['cName']) . '-m' . $rsMerchantData['nMerchantID'] . '.php';

if ($cURIActual != $cURIExpected) {
	header("Location:  $cURIExpected", TRUE, 301);
	exit();
} // ends if ($cURIActual != $cURIExpected)

Here’s the simplify function:

function simplify($cString, $bNoDashes = false) {
	$cString = str_replace("'", '', $cString);
	$cString = preg_replace("/[^A-Za-z0-9]/", "-", $cString);
	$cString = str_replace('--', '-', $cString);
	$cString = str_replace('--', '-', $cString);
	$cString = str_replace('--', '-', $cString);
	$cString = str_replace('--', '-', $cString);
	$cString = preg_replace("/\-$/", "", $cString);
	if ($bNoDashes) {
		return str_replace('-', '', $cString);
	} // ends if ($bNoDashes)
	else {
		return $cString;
	} // ends else from if ($bNoDashes)
} // ends function urlfriendly($cString)

Hopefully you can follow the PHP coding.

So if you have a large database-driven site, you can use wildcard DNS to create the appearance of many, many subdomains. Just be sure to put checks in place, so you don’t have thousands of copies of the page across all of the subdomains.