Conditional RewriteBase

Question

I'm using Apache 2.4 with mod_rewrite, and I have a problem I can't solve.

I have a .htaccess file containing

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /

    ... RewriteRules ...
</IfModule>

This works nicely. Now I need to do the following: If somebody accesses my website as http://my.web.page.com, I need RewriteBase / as in the example above. But if somebody accesses the website as http://192.168.1.10/xyz, I need RewriteBase /xyz instead.

I guess I can use <If expression>...</If> to achieve this, but I've not been able to write the expression correctly.

The xyz is a fixed string. It doesn't have to be copied from the URL, but can be hard-coded in the RewriteBase /xyz command.

How can I do this?

EDIT

@anubhava suggested an expression, which I couldn't get to work. So I tried some very simple <If...> statements that simply use the RewriteBase / statement.

I am now very, very confused.

Attempt 1

RewriteEngine On
RewriteBase /

<If "false">
  RewriteBase /
</If>

This works. So far so good. Now let's enable the conditional:

Attempt 2

RewriteEngine On
RewriteBase /

<If "true">
  RewriteBase /
</If>

This does not work. So enabling the conditional makes a difference. Perhaps the two RewriteBase statements cause the code to fail.

Attempt 3

RewriteEngine On

<If "true">
  RewriteBase /
</If>

Nope, this still doesn't work. Perhaps it is the mere presence of the conditional that is a problem?

Attempt 4

RewriteEngine On
RewriteBase /

<If "true">
  #RewriteBase /
</If>

This works. So the conditional itself is harmless. I just can't write RewriteBase inside it.

For completeness sake, the rewrite rules I'm using are:

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

The Apache error log contains no error information.

SECOND EDIT

Based on the suggestions from @anubhava, I managed to get this to work:

RewriteEngine On
RewriteBase /

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]

# case 1
RewriteCond %{HTTP_HOST} =my.web.page.com
RewriteRule ^(.*)$ index.php?/$1 [L,QSA]

# case 2
RewriteCond %{HTTP_HOST} ^192\.168\.
RewriteRule ^(.*)$ xyz/index.php?/$1 [L,QSA]

Answer 1

Based on your edited question these rules should work:

RewriteEngine On 
RewriteBase /

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]

# case 1
RewriteCond %{HTTP_HOST} =my.web.page.com
RewriteRule ^(.*)$ index.php?/$1 [L,QSA]

# case 2
RewriteCond %{HTTP_HOST} ^192\.168\.
RewriteRule ^(.*)$ xyz/index.php?/$1 [L,QSA]