虚拟主机不支持子目录的情况下借助.htaccess实现多个域名重定向到子目录实现单空间多站点

举例：
有多个域名：site1.haoduck.com，site2.haoduck.com，site3.haoduck.com
分别在二级目录site1.haoduck.com/，site2.haoduck.com/，site3.haoduck.com/

.htaccess的代码如下

1. RewriteEngine On
2. RewriteCond %{HTTP_HOST} ^site1.haoduck.com$
3. RewriteCond %{REQUEST_URI} !^/site1.haoduck.com/
4. RewriteCond %{REQUEST_FILENAME} !-f
5. RewriteCond %{REQUEST_FILENAME} !-d
6. RewriteRule ^(.*)$ /site1.haoduck.com/$1
7. RewriteCond %{HTTP_HOST} ^site1.haoduck.com$
8. RewriteRule ^(/)?$ site1.haoduck.com/index.php [L]
9.  
10. RewriteCond %{HTTP_HOST} ^site2.haoduck.com$
11. RewriteCond %{REQUEST_URI} !^/site2.haoduck.com/
12. RewriteCond %{REQUEST_FILENAME} !-f
13. RewriteCond %{REQUEST_FILENAME} !-d
14. RewriteRule ^(.*)$ /site2.haoduck.com/$1
15. RewriteCond %{HTTP_HOST} ^site2.haoduck.com$
16. RewriteRule ^(/)?$ site2.haoduck.com/index.php [L]
17.  
18. RewriteCond %{HTTP_HOST} ^site3.haoduck.com$
19. RewriteCond %{REQUEST_URI} !^/site3.haoduck.com/
20. RewriteCond %{REQUEST_FILENAME} !-f
21. RewriteCond %{REQUEST_FILENAME} !-d
22. RewriteRule ^(.*)$ /site3.haoduck.com/$1
23. RewriteCond %{HTTP_HOST} ^site3.haoduck.com$
24. RewriteRule ^(/)?$ site3.haoduck.com/index.php [L]