How to set up WordPress Multisite in Plesk using sub-directories?

Question

How to set up WordPress Multisite in Plesk using sub-directories?

Answer

1. Log into Plesk

2. Go to Domain > example.com > Install WordPress;

   Note: This step can be skipped if WordPress is already present on the domain.

3. Make sure Multisite feature was enabled after WordPress installation in Domains > example.com > File Manager > wp-config.php:

   Before:

   CONFIG_TEXT: /* That's all, stop editing! Happy publishing. */

   After:

   CONFIG_TEXT: define('WP_ALLOW_MULTISITE', true);
   
   /* That's all, stop editing! Happy publishing. */

   This line enables multisite network feature.

4. Log into WordPress through Domains > example.com > Log in;

5. In WordPress Administrator Dashboard open Tools > Network setup;

6. Set Addresses of Sites in your Network to Sub-directories and click Install;

7. Copy the suggested configuration and add it in Domains > example.com > File Manager for wp-config.php and .htaccess files.

   This is an example for wp-config.php:

   Before:

   CONFIG_TEXT: /* That's all, stop editing! Happy publishing. */

   After:

   CONFIG_TEXT: define('MULTISITE', true);
   define('SUBDOMAIN_INSTALL', false);
   define('DOMAIN_CURRENT_SITE', 'example.org');
   define('PATH_CURRENT_SITE', '/');
   define('SITE_ID_CURRENT_SITE', 1);
   define('BLOG_ID_CURRENT_SITE', 1);
   /* That's all, stop editing! Happy publishing. */

   This is an example for .htaccess file:

   Before:

   CONFIG_TEXT: # BEGIN WordPress
   # The directives (lines) between "BEGIN WordPress" and "END WordPress" are
   # dynamically generated, and should only be modified via WordPress filters.
   # Any changes to the directives between these markers will be overwritten.
   <IfModule mod_rewrite.c>
   RewriteEngine On
   RewriteBase /
   RewriteRule ^index\.php$ - [L]
   RewriteCond %{REQUEST_FILENAME} !-f
   RewriteCond %{REQUEST_FILENAME} !-d
   RewriteRule . /index.php [L]
   </IfModule>
   # END WordPress

   After:

   CONFIG_TEXT: # BEGIN WordPress
   # The directives (lines) between "BEGIN WordPress" and "END WordPress" are
   # dynamically generated, and should only be modified via WordPress filters.
   # Any changes to the directives between these markers will be overwritten.
   <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

8. Set up additional directives to enable Multisite redirects:

   Note: nginx serves dynamic content when Proxy mode is present and set to disabled state in Domains > example.com > Apache & nginx Settings:
   

   In case dynamic content is served by nginx

   1. Log into Plesk;

   2. Go to Domains > example.com > Apache & nginx Settings;

   3. Add the following to the Additional nginx directives:

      CONFIG_TEXT: rewrite ^/([_0-9a-zA-Z-]+)/wp-admin$ /$1/wp-admin/index.php;
      rewrite ^/([_0-9a-zA-Z-]+)/wp-admin/$ /$1/wp-admin/index.php;
      rewrite ^/([_0-9a-zA-Z-]+)/((wp-(?:content|includes|admin)).*)$ /$2 break;
      if ($request_uri !~ "^/(wp-(?:content|includes|admin)).*") {
      rewrite ^/([_0-9a-zA-Z-]+)/(.*\.php)$ /$2 break;
      }
      set $test "";
      if (!-e $request_filename) {
      set $test P;
      }
      if ($uri !~ ^/(plesk-stat|webstat|webstat-ssl|ftpstat|anon_ftpstat|awstats-icon|internal-nginx-static-location)) {
      set $test "${test}C";
      }
      if ($test = PC) {
      rewrite ^/.*$ /index.php;
      }

   In case dynamic content is served by Apache Web Server

   1. Log into Plesk;
   2. Go to Domains > example.com > Apache & nginx Settings;

   3. Disable Static files processing (if present) and Apply the settings.

9. Re-login to the WordPress instance as an administrator in  Domains > example.com > Log in next to WordPress instance

10. Go to My Sites > Network Admin > Sites:
    
11. Create additional sites in the WordPress network by clicking Add New:
    
    Multisite feature can be used from this point at the following URLs (example ones): 
    - http://example.com/site1
    - http://example.com/site2