PHP float numbers not adding correctly - decimal value missing

Question

I am trying to get the total of my variables containing numbers, some may be decimals. I need this to be to two decimal places and am using the number_format() function.

$total =  $order->order->net+$order->order->deductions+$order->order->vat+$order->order->postage+$order->order->postage_tax; 
            echo number_format((float)$total, 2, '.', '');?>

I have noticed the following values do not add up correctly and seems to be ignoring the decimal. The total should be 118.50 but instead I get 118.00.

100+0+17.5+1+0

I have researched this and found the below

http://floating-point-gui.de/basic/

I am a little confused by it. Can anyone explain what I need to do?

*EDIT Below is dump of the $order variable showing the numbers I am trying to add up. You can see the 17.5 is 17.5 and not 17. Is it because they are specified as being strings perhaps?

object(SimpleXMLElement)#12 (21) { ["id"]=> string(6) "922704" ["shopkeeper_orderno"]=> string(4) "1001" ["customer"]=> string(6) "797893" ["creationdate"]=> string(16) "29-05-2012 11:55" ["net"]=> string(3) "100" ["vat"]=> string(4) "17.5" ["status"]=> string(1) "1" ["isnew"]=> string(1) "0" ["deductions"]=> string(1) "0" ["postage"]=> string(1) "1" ["paymentmethod"]=> string(20) "PayPal " ["instructions"]=> object(SimpleXMLElement)#17 (0) { } [2]=> object(SimpleXMLElement)#22 (1) { ["items"]=> object(SimpleXMLElement)#30 (9) { ["id"]=> string(7) "1384486" ["headerID"]=> string(6) "922704" ["productID"]=> string(7) "4959678" ["description"]=> string(13) "Wedding dress" ["net"]=> string(3) "100" ["vat"]=> string(4) "17.5" ["qty"]=> string(1) "1" ["formID"]=> string(2) "-1" ["options"]=> object(SimpleXMLElement)#31 (1) { ["options"]=> array(2) { [0]=> object(SimpleXMLElement)#32 (6) { ["id"]=> string(6) "519981" ["orderDetailsID"]=> string(7) "1384486" ["optionid"]=> string(6) "646934" ["optionCost"]=> string(1) "0" ["optionVAT"]=> string(1) "0" ["customText"]=> string(9) "size : 12" } [1]=> object(SimpleXMLElement)#33 (6) { ["id"]=> string(6) "519982" ["orderDetailsID"]=> string(7) "1384486" ["optionid"]=> string(6) "647285" ["optionCost"]=> string(1) "0" ["optionVAT"]=> string(1) "0" ["customText"]=> string(14) "Colour : Ivory" } } } } } } ["postage_tax"]=> string(1) "0" ["dispatched"]=> string(1) "0" ["paybyotherid"]=> string(2) "-1" ["wheredidyouhearid"]=> string(2) "-1" }

Answer 1

you can use round and then number format:

  $total = 100+0+17.5+1+0.2;
//echo number_format((float)$total);  //119
  echo number_format(round((float)$total,2),2);  //118.50