cPanel - .htaccess point to subdomain

Question

I have 2 domains point to the same hosting.

domain_a.com & domain_b.com

The domain_b.com is actually point to subdomain of domain_a.com (i.e. domain_b.domain_a.com)

Directory structure

public_html
 |
 |---- domain_a
 |---- domain_b
 |---- ...
 |---- .htaccess

Content of .htaccess is

AddHandler application/x-httpd-php54 .php

RewriteEngine on
RewriteCond %{HTTP_HOST} ^(www.)?domain_a.com$
RewriteCond %{REQUEST_URI} !^/domain_a/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /domain_a/$1
RewriteCond %{HTTP_HOST} ^(www.)?domain_a.com$
RewriteRule ^(/)?$ domain_a/index.html [L] 

However, my domain_b.com actually is using ZendFramework 2. Which have the document root on public dir

i.e.

public_html
  |
  |---- domain_a
  |---- domain_b
          |---- public  <------ HERE
  |---- ...
  |---- .htaccess

At the end, I get this result

Any idea?

Edit

# Use PHP5.4 as default
AddHandler application/x-httpd-php54 .php

RewriteEngine on

RewriteCond %{HTTP_HOST} ^(www.)?domain_a\.com$
RewriteRule !^domain_a(/|$) /domain_a%{REQUEST_URI} [L,NC]

RewriteCond %{HTTP_HOST} ^(www.)?domain_b\.com$
RewriteRule !^domain_b/public(/|$) /domain_b/public%{REQUEST_URI} [L,NC]

This cause the error Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace.

In domain_b/public also has a .htaccess file. This is default from Zend Framework 2

RewriteEngine On
# The following rule tells Apache that if the requested filename
# exists, simply serve it.
RewriteCond %{REQUEST_FILENAME} -s [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]
# The following rewrites all other queries to index.php. The 
# condition ensures that if you are using Apache aliases to do
# mass virtual hosting, the base path will be prepended to 
# allow proper resolution of the index.php file; it will work
# in non-aliased environments as well, providing a safe, one-size 
# fits all solution.
RewriteCond %{REQUEST_URI}::$1 ^(/.+)(.+)::\2$
RewriteRule ^(.*) - [E=BASE:%1]
RewriteRule ^(.*)$ %{ENV:BASE}index.php [NC,L]

Answer 1

Solve this by setting the path of subdomain to domain_b/public/ during subdomain creation.

Answer 2

Try these rules:

RewriteEngine on

RewriteCond %{REQUEST_FILENAME} -s [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]

RewriteCond %{HTTP_HOST} ^(www.)?domain_a\.com$
RewriteRule !^domain_a(/|$) /domain_a%{REQUEST_URI} [L,NC]

RewriteCond %{HTTP_HOST} ^(www.)?domain_b\.com$
RewriteRule !^domain_b/public/index\.php(/|$) /domain_b/public/index.php [L,NC]