Topic on Extension talk:Cognitive Process Designer/Flow

As soon as I add the line:

wfLoadExtension( 'CognitiveProcessDesigner' );

to LocalSettings.php after installation I get a white screen of death. I have Semantic MediaWiki setup and running.

debian 9 vm with 1GB RAM

MediaWiki 1.35.0

PHP 7.3.23-1+0~20201008.68+debian9~1.gbp30f6c3 (apache2handler)

MariaDB 10.1.45-MariaDB-0+deb9u1

ICU 65.1

Timeless theme.

Error message in /var/log/apache2/error.log:

[Sun Oct 11 11:21:22.333788 2020] [php7:error] [pid 1202] [client 192.168.1.2:56948] PHP Fatal error:  Uncaught Error: Class 'WebRequest' not found in /var/www/html/wiki/includes/HeaderCallback.php:63\nStack trace:\n#0 [internal function]: MediaWiki\\HeaderCallback::callback()\n#1 {main}\n  thrown in /var/www/html/wiki/includes/HeaderCallback.php on line 63

Anything very obviously wrong?

I know the question is 2 years old, but I had the same problem. The PHP Error Log answered it, the extension needs the PageForms extension installed too.