get_order_discount return value of 0,00 €

I looked deeper into the issue. Sometimes the $discount_value as returned by this line:
$discount_value = $this->export->order->get_total_discount( false );
equals
$discount_value = (float) 1.7763568394003E-15

I googled for this number (75k results ?? Turns out that this is 0 but php is not able to check this, because floating point is not accurate enough:

* https://board.phpbuilder.com/showthread.php?10287705-Weird-math-results
* https://forums.devshed.com/php-development-5/1-1-equals-0-a-384040.html
* https://stackoverflow.com/a/15383936/1129950

I think instead of comparing against != 0 the code should rather compare if the discount is greater/equals a cent or so.

I did a PR:
https://github.com/wpovernight/woocommerce-pdf-invoices-packing-slips/pull/12

Thanks for the heads up on this issue! It’s a bit of a cascading issue, in essence being a PHP issue and more of a WooCommerce issue than a PDF Invoice issue, but it doesn’t hurt to round before checking.

fixed ??

Ewout