CodeIgniter htaccess and URL rewrite issues

This simple .htaccess will remove your index.php

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

Change your check function like this

 public function check(){
    $this->load->model('check');
    $logcheck = $this->check->check($this->input->post('username'),$this->input->post('password'));

    if($logcheck == "admin"){
        //may  be you need to set login credential into session
        redirect('Phonebook/home/');
        //$this->load->view('home');
    }else{
        $this->load->view('login');
    }
}

and your home function will be like this

public function home(){
      //remember you need to check login validation from session
      $this->load->view('home');
}

to use redirect function remember you have url helper loaded.
May be this help you

https://www.example.com/index.php?/my-seo-friendly-uri

This URL contains a query string and so requires a slightly different rule in order to match it. The RewriteRule pattern matches against the URL-path only (just index.php in this case). The query string is available in its own variable.

Add the following, before your existing directives (in addition to the directive that matches /index.php/my-seo-friendly-url - which is passed as path-info):

# Redirect URLs of the form "/index.php?/my-seo-friendly-uri"
# And "/?/my-seo-friendly-uri"
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteCond %{QUERY_STRING} ^(/.*)
RewriteRule ^(index.php)?$ %1 [QSD,R=302,L]

The query string is captured (2nd condition), and the backreference (%1) is used to construct the redirect.

The first condition that checks against the REDIRECT_STATUS environment variable is required in order to prevent a redirect loop, since you appear to be using the query string method to route the codeigniter URLs in the later rewrite. The REDIRECT_STATUS env var is empty on the initial request, but set to "200" (as in 200 OK HTTP status) after the first successful rewrite.

The QSD flag (Apache 2.4+) is required to discard the original query string from the redirected request. If you are still on Apache 2.2 then append a ? (empty query string) to the substitution string instead. ie. %1?

By making the match for index.php optional (ie. ^(index.php)?$) it will also canonicalise URLs that omit index.php, but still include the query string (that may or may not currently be a problem). eg. /?/my-seo-friendly-uri.

Note that this is currently a 302 (temporary) redirect (as is your existing redirect). Only change this to a 301 (permanent) redirect once you have confirmed it works OK. 301s are cached persistently by the browser so can make testing problematic.

Summary

Your .htaccess file should look like this:

RewriteEngine On

# Query string...
# Redirect URLs of the form "/index.php?/my-seo-friendly-uri"
# And "/?/my-seo-friendly-uri"
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteCond %{QUERY_STRING} ^(/.*)
RewriteRule ^(index.php)?$ %1 [QSD,R=302,L]

# Path-Info...
# Redirect URLs of the form "/index.php/my-seo-friendly-uri"
# Also handles "/index.php" only
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^index.php(?:/(.*))?$ /$1 [R=302,L]

# CodeIgniter Front-controller
# (NB: Using query string method to pass the URL)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule (.*) index.php?/$1 [L]

Additional notes...

• The <IfModule> wrapper is not required.
• (.*) is the same as ^(.*)$ since regex is greedy by default.
• I've modified your existing path-info redirect (ie. /index.php/foo) to also redirect requests for /index.php only. This now requires an additional condition to avoid a redirect loop.

• Your CodeIgniter front-controller is using the query string method to pass /my-seo-friendly-url to the backend (as used in the question). However, you have set $config['uri_protocol'] = 'REQUEST_URI'; - which contradicts with this (although shouldn't necessarily be a problem). However, if you are using the REQUEST_URI method then you can remove the ?/$1 part from the end of the final RewriteRule substitution string. For example:

  For example, from this:

  RewriteRule (.*) index.php?/$1 [L]
  

  To this:

  RewriteRule . index.php [L]