Wordpress/Codeigniter URL issues when installed on same server

[admin]

I have installed my wordpress installation on my server root <strong>e.g mydomain.com</strong> &amp; codeigniter installed in subdirectory named ci <strong>e.g mydomain.com/ci</strong>. When I try to access my wordpress site it works fine, but when I try to access any of my ci controllers e.g mydomain.com/ci/signup it throw 404 Page Not Found CI error. but it worked fine for my default home controller. I have searched for solution &amp; tried many of them but any one of them is not worked in my case.

here is the rewrite rules in .htaccess for my both installtion.

<strong>mydomain.com/.htaccess</strong>

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

<strong>mydomain.com/ci/.htaccess</strong>

 RewriteEngine on
 RewriteBase /ci
 RewriteCond $1 !^(index\.php|user_guide|robots\.txt)
 RewriteCond %{REQUEST_FILENAME} !-f
 RewriteCond %{REQUEST_FILENAME} !-d 
 RewriteRule ^(.*)$ index.php/$1 [L,QSA]