i want to redirect domain domain1.com to domain2.com completely but without changing domain1.com URL. i thought i could do that with .htaccess but i found out that it is not po
If both domains point at the same server then you can setup your apache config to point both domains at the same document root.
NameVirtualHost *
ServerName domain1.com
DocumentRoot /www/mysite
ServerName domain2.com
DocumentRoot /www/mysite
However, I would recommend domain2.com redirects (with a 302 redirect in the .htaccess) because it will improve your search engine optimisation, as both sites will be considered as one. So if a GoogleBot finds domain2.com as a link in another site, it will add it as a pagerank to domain1.com.