When I host my website I can acess homepage but I get 404 acessing secundary pages

I’m doing a website, and now I hosted it in a free host service just to do some tests.

And I’m having a problem that I don’t have in localhost.

The problem is: I can access my homepage successfully, but whenever I try to access a secondary page I get a 404 error "http://error404.000webhost.com/? ".

I don’t see why I’m getting this error, in localhost everything works perfectly, so I will put below my code that I think that can be related to this issue.

Any help will be very welcome.

My Home() function that I call in my index.php file with my query string:

function Home(){
$url = $_GET['url'];
$url = explode('/', $url);
$url[0] = ($url[0] == NULL ? 'index' : $url[0]);

if(file_exists('inc/'.$url[0].'.php')){
    require_once('inc/'.$url[0].'.php');
}
elseif(file_exists($url[0].'/'.$url[1].'/'.$url[2].'.php')){
    require_once($url[0].'/'.$url[1].'/'.$url[2].'.php');
}
elseif(file_exists($url[0].'/'.$url[1].'.php')){
    require_once($url[0].'/'.$url[1].'.php');
}

else{
    require_once('inc/404.php');
}
}

My htaccess file:

  RewriteBase / (we need to use this in 1st htaccess line in the host Im testing)
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule ^(.*)$ index.php?url=$1 

How I acess my secundary pages: (In this case my teachers/documents secundary page)

<li class="item_menu">
     <a href="javascript:void(0);">Teachers</span></a>
     <ul>
        <li>
           <a href="<?php echo BASE;?>/teachers/documents">&nbsp;Documents</a>
        </li>
     </ul>
</li>

My BASE variable:

In localhost:

define('BASE', 'htp://localhost/website');

When I host my project in a host service:

define('BASE','http://myhostexample.org');

Is the web host case-sensitive, and are the directory names created in the correct case to match your code?

Thanks for your answer. I dont find that information anywhere if the web host is case-sensitive. And I uploaded all my files into public_html directory as this host service says! And I can acess my homepage, only can´t acess my secundary pages.