PHP bcdiv() division by zero on large numbers

Question

The following code gives "Warning: bcdiv() [function.bcdiv]: Division by zero in ..."

$a = 20000000000000002;
$b = 20000000000000004;
echo bcdiv($a, $b);

Why does this happen?

If I put the values in "" then it doesn't give a warning.

Because the bcmath library (http://www.php.net/manual/en/intro.bc.php) works with strings; not integers that fall outside of the 32-bit integer range as yours do — Mark Baker, Mar 12 '13 at 08:54

score 1 · Answer 1 · answered Mar 12 '13 at 08:55

You wrote your numbers as integers and in PHP those are way too high and are truncated to max possible integer value. BCMath works with strings. If you work with numbers that high, always make sure to put them in quotes to be sure that they really are strings.

score 0 · Answer 2 · edited Mar 12 '13 at 09:14

string bcdiv ( string $left_operand , string $right_operand [, int $scale ] )

Reference - http://www.php.net/manual/en/function.bcdiv.php

Look at the parameters and type -

left_operand

The left operand, as a string.

right_operand

The right operand, as a string.

scale

This optional parameter is used to set the number of digits after the decimal place in the result. You can also set the global default scale for all functions by using bcscale().

score 0 · Answer 3 · answered Mar 12 '13 at 08:55

According to the docs, bcdiv takes strings:

string bcdiv ( string $left_operand , string $right_operand [, int $scale ] )

Apparently, the integer values you are providing are too large for standard PHP ints to hold that value. bcmath works on strings (which is actually not so strange):

For arbitrary precision mathematics PHP offers the Binary Calculator which supports numbers of any size and precision, represented as strings.

(from the bcmath intro)

score 0 · Answer 4 · answered Mar 12 '13 at 08:55

0

BCMath functions all accept strings as arguments, so putting them in quotes is what you want to do.

BCMath documentation can be found at: http://www.php.net/manual/en/book.bc.php

answered Mar 12 '13 at 08:55

shannonman

841
4
8

score 0 · Answer 5 · answered Mar 12 '13 at 09:15

You were correct to wrap them in "" as bcdiv wants the inputs as strings

string bcdiv ( string $left_operand , string $right_operand [, int $scale ] )