Warning: A non-numeric value encountered

Question

Recently updated to PHP 7.1 and start getting following error

Warning: A non-numeric value encountered in on line 29

Here is wha

Answer 1

You can solve the problem without any new logic by just casting the thing into the number, which prevents the warning and is equivalent to the behavior in PHP 7.0 and below:

$sub_total += ((int)$item['quantity'] * (int)$product['price']);

(The answer from Daniel Schroeder is not equivalent because $sub_total would remain unset if non-numeric values are encountered. For example, if you print out $sub_total, you would get an empty string, which is probably wrong in an invoice. - by casting you make sure that $sub_total is an integer.)