Website is not accessible: Increasing max input vars limit needed

Symptoms

The website is not accessible. The following error is shown in the browser screen:

PHP Max Input Vars: [?] 1000 - Recommended Value: 3000. Max input vars limitation truncate POST data such as menus. Increasing max input vars limit needed.

Cause

Default value for max_input_vars directive is insufficient.

Resolution

1. Log into Plesk.

2. Increasemax_input_vars parameter in Domains > example.com > PHP Settings > Additional configuration directives:
   

   NOTE: If there is no Additional configuration directives in PHP settings, contact your system administrator.