CODEWITHSUNDEEP
phpmathroundingadditionsubtraction
Ben Wilson
Ben Wilson

Reputation: 2676

Numeric values rounding down unexpectedly

I have a loop that calculates a couple revenue values then adds them together, like this:

$SalesGrowth = $C2012Sales+$C2011Sales;

In some cases, this works, and I get the expected, e.g.: 761.9 + 759.0 = 1520.9

In others, it looks like PHP randomly decides to round incorrectly (??) AND change the units (??) and I get:

8,788.0 + 8,794.3 = 16

What is going on here? I've even tried echoing out the separate sales values separated by a space, and they show up correctly, so the underlying figures aren't wrong.

Upvotes: 1

Views: 157

Answers (4)

Kerrek SB
Kerrek SB

Reputation: 477268

Interpreted as a number, 8,788.0 is just 8, and parsing stops at the comma.

You'll need some locale-aware number parsing if you want to allow gimmicks like thousands-separators.

Update: If you have the Zend Framework, you can do this:

require_once('Zend/Locale/Format.php');

$locale = new Zend_Locale('en_GB'); // #1

$v = "8,410.5";
$n = Zend_Locale_Format::getNumber($v, array('locale' => $locale,'precision' => 3));

echo 2 * $number;   // prints "16821"

Instead of hard-coding the locale, you could try and take it from the environment: new Zend_Locale(setlocale(LC_ALL, ""))

Upvotes: 9

ash108
ash108

Reputation: 1761

Notice that 761.9 is a valid number, while 8,788.0 is not (from PHP's point of view).

So 8,788.0 in number context will evaluate as 8, just like 8,794.3. And 8+8 = 16.

To fix this problem, process your data to make numbers formatted properly.

Upvotes: 2

Rajat Singhal
Rajat Singhal

Reputation: 11264

Dude the comma issue....

remove all the commas from the numbers before adding them...

str_replace(",","",$no1);

Upvotes: 3

gahooa
gahooa

Reputation: 137412

This is pretty simple... When you ask PHP to use the + operator, it will implicitly convert these strings such as "8,788.0" to an numeric value. Since you have a , character, it terminates the usefulness of the number, and it results in it being interpreted as 8. And so on...

Get rid of the non [0-9.] characters and it will work better.

Upvotes: 2

Related Questions