Can't include wp-blog-header.php in external plugin's file under multisite

I create a plugin, and it needs to have a php file, which needs be launched by CRON. And this php file need to use native WP functions.

To include this ability in that php file, I use the following code:

$file_root_directory = dirname(__FILE__); //get current file direct path

$target_string_array = explode('wp-content', $file_root_directory); //it is the way, how I get site directory

require_once ($target_string_array[0] . 'wp-blog-header.php'); //include native wp functions

This code works good when I use the plugin on usual single site installation.
But, when I install this plugin on multisite network and try to launch that php file – the script just breaks execution on line with “require_once” without even any error.

If I try to include any other php files – they are included successfully (these files just contain php functions and do nothing until they are not called).

How I understood that php file aborted execution on line with include “wp-blog-header.php”, despite the script does not generate any error:

I just used this code and made a log:

file_put_contents(dirname(__FILE__) . '/log.txt', 'point 1' . "\r\n\r\n", FILE_APPEND);

$file_root_directory = dirname(__FILE__); //get current file direct path

file_put_contents(dirname(__FILE__) . '/log.txt', 'point 2' . "\r\n\r\n", FILE_APPEND);

$target_string_array = explode('wp-content', $file_root_directory); //it is the way, how I get site directory

file_put_contents(dirname(__FILE__) . '/log.txt', 'point 3' . "\r\n\r\n", FILE_APPEND);

require_once($target_string_array[0] . 'wp-blog-header.php'); //include native wp functions

file_put_contents(dirname(__FILE__) . '/log.txt', 'point 4' . "\r\n\r\n", FILE_APPEND);

The last point was “point 3”.

Due to the fact, that the plugin works successfully on my local server (both – on single installation and multisite mode) but refuses to work on external server, I decided that the problem is in wp-config.php or in .htaccess files (apparently, some of the apach module that causes that bug in external server is disabled in the local server)

But I can’t see any suspicious in those files.

In the wp-cofig.php I aded the following lines (accordingly to the multisite installation guide):

define('WP_ALLOW_MULTISITE', true);

define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', false);
define('DOMAIN_CURRENT_SITE', 'site-name.org');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

just before comment line:

/* That's all, stop editing! Happy blogging. */

The .htaccess looks like the following:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]
</IfModule>

# END WordPress

On the local server and on the external server I use Sub-Directory for sites in network. And all other plugin’s functionality works properly on both (like a wp hooks, sending data, working with database, etc). The problem is only when I try to launch that file, and exactly during including wp-blog-header.php, and only in external server.

Any one have some ideas, where I should to dig?