FAQ #5 Implementation

On the Post Reorder page I would like the newly published post to show up first rather than last. I tried putting the filter code from FAQ number 5 in my theme function PHP file but got errors:

Uncaught Error: Call to undefined function filter() in wp-content/themes/voice/functions.php:187
Stack trace:
#0 wp-settings.php(546): include()
#1 wp-config.php(80): require_once('/home/customer/...')
#2 wp-load.php(50): require_once('/home/customer/...')
#3 wp-admin/admin.php(34): require_once('/home/customer/...')
#4 wp-admin/theme-editor.php(10): require_once('/home/customer/...')
#5 {main}
  thrown

How do I implement the fix so a new post will show up first vs last, without pushing the reorder button and having to resort all my adjustments each time?