Unable to process certain action in WordPress: POST Content-Length of 9795417 bytes exceeds the limit of 8388608 bytes

Symptoms

• Unable to upload a file or edit a page via a WordPress plugin builder for the domain example.com;
• The error like the one below or a similar is logged in the error logs:

  CONFIG_TEXT: Got error 'PHP message: PHP Warning: POST Content-Length of 9795417 bytes exceeds the limit of 8388608 bytes in Unknown on line 0', referer: https://example/wp-admin/theme-install.php?browse=popular

Cause

Low values for the post_max_size and upload_max_filesize PHP variables.

Resolution

Increase the values for the specific variables: 

1. Log into Plesk;

2. Go to Domains > example.com > PHP Settings;

3. Increase value for the post_max_size and upload_max_filesize directives;

4. Scroll down and press the OK button to apply the changes.