Mulitple sites, single application

[eluser]Animas[/eluser]
Yes, I can use single CI for multiple apps. But my need is a bit different. I have sites site1.com, site2.com and site3.com. All sites will show same content that means will use same(single) application (parking purpose). But the problem is in app's config.php we need to define $config['base_url']. Can I use multiple $config['base_url'] as below?

Code:

$config['base_url']="http://www.site1.com/";
$config['base_url']="http://www.site2.com/";
$config['base_url']="http://www.site3.com/";