Point 2 domains on the same hosting to different files - apache

Question

I'm having an issue with .htaccess.
I have 3 Domains in one Webspace, all directed to the same content: (www.domain1.com, www.domain2.com, www.domain3.com).
Now I want only the www.domain1.com to start with my WordPress site(index.PHP), the other two domains should start with index.HTM, but I don't want to create subfolders, because all Domains shall have access to the same .htm-Files in the root directory – ONLY the start files (index.php/index.htm) should be different. Is it possible to realize this, for example with mod_rewrite in the htaccess? I tried and failed.
RewriteEngine on
RewriteCond %{HTTP_HOST} ^www.domain1.com
RewriteRule ^/$ /index.php [L]
RewriteCond %{HTTP_HOST} ^www.domain2.com
RewriteRule ^/$ /index.htm [L]
RewriteCond %{HTTP_HOST} ^www.domain3.com
RewriteRule ^/$ /index.htm [L]

Answer 1

I managed to find a solution to my problem using PHP instead of .htaccess. It was not the neatest solution but it solves my issue:
switch ($_SERVER ["HTTP_HOST"]) {
case "www.domain1.com":
if ($_SERVER['SCRIPT_URL'] == '/') {
header("Location: http://www.domain1.com/index.php");
} else {
header("Location: {$_SERVER['SCRIPT_URL']}");
}
break;
case "www.domain2.com":
if ($_SERVER['SCRIPT_URL'] == '/') {
header("Location: http://www.domain2.com/index.htm");
} else {
header("Location: {$_SERVER['SCRIPT_URL']}");
}
break;
case "www.domain3.com":
if ($_SERVER['SCRIPT_URL'] == '/') {
header("Location: http://www.domain3.com/index.htm");
} else {
header("Location: {$_SERVER['SCRIPT_URL']}");
}
}