Accessing PHP files on another http host, on the same server

We're working on a project where we're going to be launching multiple domains/microsites that will be hosted on the same Linux server. We're wanting to have one/separate http host account act as the "storage area" for the various include files, style sheets, JS, etc that act as the template files for each of the individual domains/microsite pages. This way all we will need to do is update the files in the "storage area" area and all of the microsites will be updated.

I'm wondering what the best way to do this is. Initially I'm thinking I just need to configure the open_basedir for each of the microsite http host accounts to include the "storage area" dir on the master http host account.

Is this the best approach for executing PHP/serverside across http host accounts? Is it safe?

Thanks for your help!