I just changed the .htaccess file contents and as shown in the following links answer. And tried refreshing the page (which didn’t work, and couldn’t find the request to my controller) it worked.

Then just because of my doubt I undone the changes I did to my .htaccess inside my public_html folder back to original .htaccess content. So it’s now as follows (which is originally it was):

DirectoryIndex index.php
RewriteEngine on
RewriteCond $1 !^(index\.php|images|css|js|robots\.txt|favicon\.ico)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ ./index.php?/$1 [L,QSA]

And now also it works.

Hint: Seems like before the Rewrite Rules haven’t been clearly setup within the Server context.

My file structure is as follows:

/
|- gheapp
|    |- application
|    L- system
|
|- public_html
|    |- .htaccess
|    L- index.php

And in the index.php I have set up the following paths to the system and the application:

$system_path="../gheapp/system";
$application_folder="../gheapp/application";

Note: by doing so, our application source code becomes hidden to the public at first.

Please, if you guys find anything wrong with my answer, comment and re-correct me!
Hope beginners would find this answer helpful.

Thanks!