CODEWITHSUNDEEP
phpmultiplicationoperation
crasholino
crasholino

Reputation: 745

Wrong multiplication in PHP

I'm trying to do a simple operation of two numbers but the operation returns a wrong result.

The number are for example 46.29 and 10. The first one in the $a variable and the second one in the $b variable.

Process

echo $a * $b

returns 460

echo 10 * 46.29

print the right number (462.90)

$a * 10

and

46.29 * $b

result is always the same: 460!

echo $a

print 46,29

echo $b

print 10

echo floatval($a) * floatval($b)

print 460

echo intval($a)

print 46

I tried also to use bcmul, and in this case it will print 0.

Here you can find my code: 

include 'simple_html_dom.php';

     $anno = $_POST['Anno'];
     $punti = $_POST['Punti'];
     $eta = $_POST['Eta'];
     $ggAss = $_POST['GgAss'];
     $ggParz1 = $_POST['GgParz1'];
     $ggParz2 = $_POST['GgParz2'];
     $ggParz3 = $_POST['GgParz3'];
     $pctDM = $_POST['PctDM'];
     $calcoloDM = $_POST['CalcoloDannoMorale'];
     $speseMediche = $_POST['SpeseMediche'];
     $spese = $_POST['Spese'];

    $html = file_get_html('..\tabella'.$anno.'.php');

    $rows = $html->find('tr');

    // This variable is use to make sure that the correct number will be display. (there is a kind of offset in the output table).
    $const = 2;


    $i = 0;
    $cond = false;
    foreach ($rows as $row) {
        $j = 0;
        foreach ($row->children() as $cell) {
            if($cond)
                break;
            //This condition is used to get punto base e indennità giornaliera
            if($i == 1) {
                $var1 = explode(" ", $cell->plaintext);
                $indennitaGG = $var1[10]; // here we can get indennità giornaliera
            }
            if($i == ($eta + $const) && $j == $punti) {
                $dannoBP = $cell->plaintext;
                $cond = true;
                break;
            }
            $j++;
        }
        $i++;
    }

    $calcIndGG = $indennitaGG * $ggAss;
    $newVar = $indennittaGG;
    echo 46.29 * 10;
    $calcIndParz1 = ($indennitaGG * 75 / 100) * $ggParz1;
    $calcIndParz2 = ($indennitaGG * 50 / 100) * $ggParz2;
    $calcIndParz3 = ($indennitaGG * 25 / 100) * $ggParz3;
    $dm = ($calcIndGG + $calcIndParz1 + $calcIndParz2 + $calcIndParz3) * $pctDM / 100;

    $totale = $dannoBP + $calcIndGG + $calcIndParz1 + $calcIndParz2 + $calcIndParz3 + $dm + $speseMediche + $spese;

What's the problem with this?

EDIT: PROBLEM SOLVED with this code:

//This change is used to transform the variable $indennitaGG in the right form. (with the . and not with the ,). Then we can make the cast to float.


    $temp = str_replace(",",".", $indennitaGG);
        $indennitaGG = (float)$temp;

Upvotes: 4

Views: 4776

Answers (4)

ForceMagic
ForceMagic

Reputation: 506

The , character is not valid for a floating point number. Try to replace it with str_replace(",",".",$a);. Even try to do it with both numbers if you wish.

The "official" decimal separator (for PHP) is a point (.), that's why it fails doing the multiplication. In your language it might be the comma, but PHP uses a dot.

This is what PHP would say (to floatval($a)):

Ok, I got two characters, which is a valid number (46), but after that there's a weird symbol, I'll just throw a warning, add a decimal point and a zero (cause I found no other decimal points), and end the conversion here.

If you use this code, it should work:

str_replace(",",".",$a);
str_replace(",",".",$b);
echo floatval($a) * floatval($b);

Explanation:

As I said, you're using a decimal comma, which is invalid. What str_replace(original, replacement, subject) does is that it finds all occurrences of original in a string (here: subject) and replaces it with the replacement value. This results in replacing that decimal comma with a decimal point.

Example: 40,3 becomes 40.3

This still results in a String data type, which is obviously not a number. To convert it, we use the method floatval(string), which results in a Float data type, which is short for Floating-point number and after that, we can perform arithmetical operations.

Upvotes: 4

Peter VARGA
Peter VARGA

Reputation: 5186

Your locale is using a different sign for the decimal point. I suspect when you read the numbers from a file they are in the "wrong" format - e.q. 46,29 and not 46.29 as I can see from the echo.

Replace the , to . and then the issue is fixed.

Upvotes: 3

Kami Yang
Kami Yang

Reputation: 427

try to cast themas a float before using them. this should probably work. If its not, what types do you get when you use var_dump()?

Upvotes: 0

Goose
Goose

Reputation: 4821

If you run this code, you'll get the correct result.

$a = 10;
$b = 46.29;
echo $a * $b;

echo $a and $b before you get to the math. If the numbers are correct, cast them like this.

echo floatval($a) * floatval($b);

If these aren't working, you'll need to give us the right code to recreate the issue. Your full code depends on post variables and an include. Give us just the code to recreate the issue.

Upvotes: 0

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