Auto redirect to 'index' file destroys HTTP_HOST

[MrCat]

I have multiple domain names pointing to the same site.

This works fine in the root folder: mysite.com and myothersite.com begin at mysite.com/index.php and I can change display settings depending on HTTP_HOST (which is either set to mysite.com or myothersite.com).

It doesn't work when I go one folder deeper: mysite.com/start and myothersite.com/start are always seen as mysite.com/start/index.php - destroying the HTTP_HOST variable.

What can I do? I'm on a shared host so can't do much in the way of config.
Any help appreciated

[Cags]

You'll need to make all the links on your site full paths, built up using the HTTP_HOST field. If you do this then the links on pages should always remain the same as the domain they originally arrived on.

[MrCat]

Thanks Cags, but the HTTP_HOST field is the problem as it doesn't contain the domain I originally arrived on.
Once Apache redirects from a folder URL to the index file URL, the HTTP_HOST reverts to the 'parent' domain and not the alias I arrived on.
I hope I'm making sense!