rewriteEngine on
rewriteCond %{http_host} ^[url]www.test.com[/url]
rewriteRule ^(.*)$ [url]http://www.abc.com/test/$1[/url]

RewriteEngine on
# 把 yourdomain.com 改为你要绑定的域名.
RewriteCond %{HTTP_HOST} ^(www.)?yourmaindomain.com$
# 把 subfolder 改为要绑定的目录.
RewriteCond %{REQUEST_URI} !^/subfolder/
# 不要改以下两行.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

# 把 subfolder 改为要绑定的目录.
RewriteRule ^(.*)$ /subfolder/$1

# 把 yourdomain.com 改为你要绑定的域名
# 把 subfolder 改为要绑定的目录.
# subfolder/ 后面是首页文件index.php, index.html.....

RewriteCond %{HTTP_HOST} ^(www.)?yourmaindomain.com$
RewriteRule ^(/)?$ subfolder/index.php [L]