Unable to access PHP Settings in Plesk: Message Cannot read properties of undefined (reading 'toLowerCase')

Symptoms

• PHP Settings page at Domains > example.com > Dashboard tab cannot be accessed with the error message:

  PLESK_INFO: Type TypeError
  Message Cannot read properties of undefined (reading 'toLowerCase')

• Proxy Mode is disabled at Domains > example.com > Hosting & DNS tab > Apache & nginx Settings.

Cause

Database inconsistency: when Proxy Mode is disabled for a domain, nginxServePhp value in the Plesk database must be set to true, but it is false:

# plesk db "select d.name, h.php_handler_id, wssp.value as nginxServePhp from domains d right join hosting h on d.id=h.dom_id right join dom_param dp on d.id=dp.dom_id right join WebServerSettingsParameters wssp on wssp.webServerSettingsId=dp.val where wssp.name='nginxServePhp' and dp.param='webServerSettingsId' and d.name = 'example.com'"

+-------------+---------------------------+---------------+
| name        | php_handler_id            | nginxServePhp |
+-------------+---------------------------+---------------+
| example.com | plesk-php82-fpm-dedicated | false         |
+-------------+---------------------------+---------------+

Resolution

1. Log in to Plesk.
2. Go to Domains > example.com > Hosting & DNS tab > Apache & nginx Settings.
3. Enable Proxy Mode under nginx Settings.
4. Go to Domains > example.com > Dashboard tab > PHP Settings.
5. Go back to Apache & nginx Settings page and disable Proxy Mode back.