Make wordpress run off two domains with same content and same database..

Using modified twentyten theme.
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Hello,

1. I installed wordpress on domainA.com, and it is fully functional and working correctly.

2. In all my posts, pages, and template code I used the following for links:
<a href="<?php get_site_url(); ?>/development.html">

3. From DNS i setup domainB.com to point to domainA.com … To my surprise when you visit either domainA or domainB .. all links point to whichever domain you are currently on.

So for example if you are on domainA then all links appears as:
<a href="http://www.domainA.com/development.html">

And if you are on domainB then all links appear as:
<a href="http://www.domainB.com/development.html">

Which is perfectly working and exactly how I wanted it to work, even though I was under the impression that domainB would make all links point to domainA because of the value it is suppose to grab from “get_site_url();”.
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Now here is my issue, when on domainB if you use the search, go to an archive page, or click on a “Read More” link … it all links back to domainA. So all links I created with “get_site_url();” correctly work no matter which domain you are on, but anything dynamically generated by WordPress only uses domainA in the link.

Is there anyway I can accomplish this? My website is is 99% done, I just need to cause the search and dynamic links to pick up the current domain URL like all the other links which work do it.

Thank you in advance.