Thanks! I'll see if I can explain it better.
Four domains totally (I haven't set them up in subdirectories...they're all on their own hosting accounts):
If a user goes to www.sub1.com, they are redirected to www.primary.com. Now this main website has general company-wide info as well as, on the main page, prominent links that go back to all three of the sub sites. The thinking is that they want users to go to the main site before heading to any of the sub sites (each sub site is location-based — different state for each).
Here's what I did: I juts put an htaccess file in the root public directory with a DirectoryIndex home.php index.php in it. The home.php file that each of the sub domains have redirects the user to the primary.com website. That website then has links that will go to www.sub1.com/index.php, etc. Since the index.php file doesn't redirect the user, they can then navigate the website normally, and any internal links back to that site's home page goes to index.php.
The one advantage to do it the way I did, that I can figure, is that employees or frequent visitors can just bookmark www.sub1.com/index.php (instead of www.sub1.com) and bypass the redirect to the main website. But I don't know if there's a big disadvantage to the way I set it up.
If there's a compelling reason for me to do this another way, I'm all for it. (While I understand why they're doing it, it seems like more of an annoyance to their users.) Otherwise, any other suggestions would be greatly appreciated.