URL mapping between 2 domains - apache

Question

We have an online service with 3 customers: Autoparts, CarExamples and Cars & More. This is the url structure:
example.com/autoparts
example.com/carexamples
example.com/carsandmore
One of the customers (CarExamples) wants to use their own domain (carexamples.com), but it has to load the content of example.com/carexamples, of course always using the original domain.
That means that:
carexamples.com should load example.com/carexamples
carexamples.com/about should load example.com/carexamples/about
carexamples.com/categories/trucks?p=1 should load example.com/carexamples/categories/trucks?p=1
We are using a LAMP environment (PHP v5.6). The domain example.com is located in /www/example/html in our server.
The current status of this issue is:
Create an A record in the domain's DNS manager console that points to the same server where example.com is being hosted.
Add a virtual host for the custom domain
<VirtualHost servername:80>
ServerName carexamples.com
ServerAlias www.carexamples.com
DocumentRoot /www/example/html
</VirtualHost>
But this would just load the same content of example.com when opening carexamples.com
It is worth noting that /www/example/html/carexamples is not a directory, it is a rewrite from /www/example/html/store.php?store=carexamples
Shopify does something similar: https://help.shopify.com/en/manual/domains/add-a-domain/using-existing-domains/connecting-domains#set-up-your-existing-domain-to-connect-to-shopify maybe that could help as a reference to this issue.
These are the existing rewrite rules in the .htaccess file:
# stores
RewriteRule ^([0-9a-zA-Z-]{2,50})$ /store.php?store=$1 [QSA,L]
# stores > categories
RewriteRule ^([0-9a-zA-Z-]{2,50})/([0-9a-zA-Z-]{1,50})$ /store.cat.php?store=$1&cat=$2 [QSA,L]
# stores > categories > items
RewriteRule ^([0-9a-zA-Z-]{2,50})/([0-9a-zA-Z-]{1,50})/([0-9]+)/([0-9a-zA-Z-]{1,100})$ /store.cat.php?store=$1&cat=$2&id_item=$3&item=$4 [QSA,L]

Answer 1

Have your rules like this in site root .htaccess:
RewriteEngine On
# per domain rewrite
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteCond %{HTTP_HOST} !^(?:www\.)?example\. [NC]
RewriteCond %{HTTP_HOST}:%{REQUEST_URI} ^(?:www\.)?([^.]+)[^:]*:(?!/\1/) [NC]
RewriteRule ^ %1%{REQUEST_URI} [L]
# stores
RewriteRule ^([\w-]{2,50})/?$ store.php?store=$1 [QSA,L]
# stores > categories
RewriteRule ^([\w-]{2,50})/([\w-]{1,50})/?$ store.cat.php?store=$1&cat=$2 [QSA,L]
# stores > categories > items
RewriteRule ^([\w-]{2,50})/([\w-]{1,50})/(\d+)/([\w-]{1,100})/?$ store.cat.php?store=$1&cat=$2&id_item=$3&item=$4 [QSA,L]

Answer 2

If I understood your post correctly (correct me or clarify if this isn't what you're looking for)
You need a separated vHost for each entry .. You're looking at the wrong directory -- This is an example -- Though it should be self explanatory .. Just add /carexamples to the DocumentRoot
<VirtualHost servername:80>
ServerName carexamples.com
ServerAlias www.carexamples.com
DocumentRoot /www/example/html/carexamples
</VirtualHost>