# BCMath Arbitrary Precision Mathematics

&reftitle.intro;

For arbitrary precision mathematics PHP offers BCMath which supports numbers of any size and precision up to `2147483647` (or `0x7FFFFFFF`) decimal digits, if there is sufficient memory, represented as strings.

Valid (aka. well-formed) BCMath numbers are strings which match the regular expression `/^[+-]?[0-9]*(\.[0-9]*)?$/`.

Passing values of type `float` to a BCMath function which expects a `string` as operand may not have the desired effect due to the way PHP converts `float` values to `string`, namely that the `string` may be in exponential notation (which is not supported by BCMath), and that, prior to PHP 8.0.0, the decimal separator is locale dependent (while BCMath always expects a decimal point).

    <?php
    $num1 = 0; // (string) 0 => '0'
    $num2 = -0.000005; // (string) -0.000005 => '-5.05E-6'
    echo bcadd($num1, $num2, 6); // => '0.000000'

    setlocale(LC_NUMERIC, 'de_DE'); // uses a decimal comma
    $num2 = 1.2; // (string) 1.2 => '1,2'
    echo bcsub($num1, $num2, 1); // => '0.0'
    ?>

&reference.bc.setup; &reference.bc.constants; &reference.bc.reference;