CODEWITHSUNDEEP
phpmathbcmath
Templar
Templar

Reputation: 1871

Why subtraction doesn't work properly using bcmath?

Let's say I have

$foo = bcsub(bcdiv(1, 3, 20), 0.00001, 20);

it returns me 0.33333333333333333333

If I have 

$foo = bcsub(bcdiv(1, 3, 20), 0.0001, 20);

it returns me 0.33323333333333333332

If I have

$foo = bcsub(0.333333333333333333, 0.00001, 20);

it returns me 0.33333333333333331483

If I have 

$foo = bcsub(0.333333333333333333, 0.0001, 20);

it returns me 0.33323333333333331482

So why it can't properly subtract, it's something with floating point? But it works fine when just bcdiv(1, 3, 20)

Upvotes: 2

Views: 1081

Answers (1)

Sjoerd
Sjoerd

Reputation: 75619

Use strings instead of floats as parameters to the BC functions:

$foo = bcsub(bcdiv("1", "3", "20"), "0.00001", "20");

If you use a float (i.e. 0.00001), PHP will convert this number to a float, which is not precise. If you use a string (i.e. "0.00001"), BC will do the conversion to an arbitrary precision number, which is precise.

Upvotes: 9

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