PHP空间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

因为手头上有10年的景安虚拟主机，不想吃灰太久，就玩了玩。

记录一下，以免忘记。

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

RewriteEngine On
RewriteCond %{HTTP_HOST} ^site1.haoduck.com$
RewriteCond %{REQUEST_URI} !^/site1.haoduck.com/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /site1.haoduck.com/$1
RewriteCond %{HTTP_HOST} ^site1.haoduck.com$
RewriteRule ^(/)?$ site1.haoduck.com/index.php [L]

RewriteCond %{HTTP_HOST} ^site2.haoduck.com$
RewriteCond %{REQUEST_URI} !^/site2.haoduck.com/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /site2.haoduck.com/$1
RewriteCond %{HTTP_HOST} ^site2.haoduck.com$
RewriteRule ^(/)?$ site2.haoduck.com/index.php [L]

RewriteCond %{HTTP_HOST} ^site3.haoduck.com$
RewriteCond %{REQUEST_URI} !^/site3.haoduck.com/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /site3.haoduck.com/$1
RewriteCond %{HTTP_HOST} ^site3.haoduck.com$
RewriteRule ^(/)?$ site3.haoduck.com/index.php [L]