renamefinal.php

<?php
   return ChangeAdminUrlPlugin::bootstrap();
    class ChangeAdminUrlPlugin {
     private $renameFrom = 'wp-admin';
     private $renameTo = 'dashboard';
     static $instance;
     static public function bootstrap() {
      null === self::$instance
       && self::$instance = new self()
       ;
      return self::$instance;
     }

     private function setCookiePath() {
      defined('SITECOOKIEPATH') || define('SITECOOKIEPATH', preg_replace('|https?://[^/]+|i', '', get_option('siteurl') . '/' ) );
      defined('ADMIN_COOKIE_PATH') || define('ADMIN_COOKIE_PATH', SITECOOKIEPATH . $this->renameTo);
     }
     public function __construct() {
      $this->setCookiePath();
      add_action('init', array($this, 'init')) ;
     }

     public function init() {
      add_filter('admin_url', array($this, 'admin_url'), 10, 3);
      add_filter('network_admin_url', array($this, 'network_admin_url'), 10, 3);//Added by Mark Figueredo, <http://gruvii.com/>
     }
     
     // OLD WAY DIDN'T CHECK FOR RELATIVE URLS
/*
     public function admin_url($url, $path, $blog_id) {
      $renameFrom = $this->renameFrom;
      $renameTo = $this->renameTo;
      $scheme = 'admin';
      $find = get_site_url($blog_id, $renameFrom.'/', $scheme);
      $replace = get_site_url($blog_id, $renameTo.'/', $scheme);
      (0 === strpos($url, $find))
       && $url = $replace.substr($url, strlen($find))
       ;
      return $url;
     }
// */
    public function admin_url($url, $path, $blog_id) {
    $renameFrom = $this->renameFrom;
    $renameTo = $this->renameTo;
    $scheme = (0 === strpos($url, '/')) ? 'relative' : 'admin';
    $find = get_site_url($blog_id, $renameFrom.'/', $scheme);
    $replace = get_site_url($blog_id,  $renameFrom.'/', $scheme);
    (0 === strpos($url, $find))
     && $url = $replace . substr($url, strlen($find))
     ;
    return $url;
	}
     public function network_admin_url($url, $path) {
      $renameFrom = $this->renameFrom;
      $renameTo = $this->renameTo;
      $scheme = 'admin';
      $find = network_site_url($renameFrom.'/', $scheme);
      $replace = network_site_url($renameTo.'/', $scheme);
      (0 === strpos($url, $find))
       && $url = $replace.substr($url, strlen($find))
       ;
      return $url;
     }
    }

#EOF;

WP_ADMIN_DIR.php

<?php

define('WP_ADMIN_DIR', 'admin');
defined('SITECOOKIEPATH') || define('SITECOOKIEPATH', preg_replace('|https?://[^/]+|i', '', get_option('siteurl') . '/' ) );
define( 'ADMIN_COOKIE_PATH', SITECOOKIEPATH . WP_ADMIN_DIR);
   
add_filter('site_url',  'wpadmin_filter', 10, 3);
 function wpadmin_filter( $url, $path, $orig_scheme ) {
  $old  = array( "/(wp-admin)/");
  $admin_dir = WP_ADMIN_DIR;
  $new  = array($admin_dir);
  return preg_replace( $old, $new, $url, 1);
}
 
function redirect_wp_admin(){
$redirect_to = $_SERVER['REQUEST_URI'];
if(count($_REQUEST)> 0 && array_key_exists('redirect_to', $_REQUEST)){
$redirect_to = $_REQUEST['redirect_to'];
$check_wp_admin = stristr($redirect_to, 'wp-admin');
if($check_wp_admin){
wp_safe_redirect( '404.php' );
}
}
}