Fatal error: Call to undefined function get_header()

Hello WordPress Developers,

I got this erros messages when I check my site like below

mysite.com/wp-content/themes/mythemes

When I visite that url, it give me this message

Fatal error: Call to undefined function get_header() in
/users/my-username/www/mysite-folder/wp-content/themes/twentyfifteen/index.php
on line 17

You know, the errors messages shouldn’t give us like that, Am I right? And I googled for this and found no better solutions. Here are some steps that I have tried

• define( ‘WP_MEMORY_LIMIT’, ‘228M’ ); (it doesn’t work)
• <?php @get_header(); ?> (it can make errors message disappear, but it is not the best solution.)
• <?php ini_set('display_errors', 0); ?> (it can also make errors disappear, but it is also not the right solutions.)
• So, I make new wordpress installation, it still give me that errors message

Please note: I don’t install any plugins

What I understand on this errors, wordpress can’t load

So, do you have better solution for this kind of errors? Please advice me, I have spent 3 hours for this.

I got your point What you are trying to do. The solution to your problem is these lines of code to place above all the code of your index file or you may place it on all files of your theme.

<?php

// Do not allow directly accessing this file.
if ( ! defined( 'ABSPATH' ) ) {
    exit( 'Direct script access denied.' );
}
?>