PHP 7.1 and Drupal commerce, navigating to /admin/commerce/orders to view orders generates the following warning:
Warning: A non-numeric value encountered in theme_pager() (line 329 of /includes/pager.inc).
This is directly the result of the new warnings in php 7.1 performing arithmetic operations on variables that are empty or not integer. While I found this in Drupal commerce, the file generating the warning is in core so I suspect the same would occur outside diurnal commerce.
The code causing the problem is:
$pager_middle = ceil($quantity / 2);
and will generate the warning if $quantity is empty. To fix the problem, I replace the line where $quantity is set :
$quantity = $variables['quantity'];
with
$quantity = empty($variables['quantity']) ? 0 : $variables['quantity'];
I have attached the patch. This is the first time I submit a patch for core, apologies if I'm not following the correct protocol.