negative zero

[raphael75]

So I have 2 arrays of numbers, and this:

$variance = array_sum($db_tot) - array_sum($cr_tot);

If the sum of each array is the same, why does PHP return -1.8189894035459E-12? Why wouldn't it be 0 (positive 0 or just 0)?

Thanks!

Edited May 1, 2014 by raphael75

[raphael75]

Figured it out - floating point math isn't straightforward. Had to use number_format to round to 2 decimal places.