数学扩展
PHP Manual

BCMath 任意精度数学

User Contributed Notes

Hayley Watson 26-Oct-2015 10:30
This extension is an interface to the GNU implementation as a library of the Basic Calculator utility by Philip Nelson; hence the name.
volek at adamv dot cz 15-Jan-2015 10:44
Note that when you use implementation of factorial that ClaudiuS made, you get results even if you try to calculate factorial of number that you normally can't, e.g. 2.5, -2, etc. Here is safer implementation:
<?php
/**
 * Calculates a factorial of given number.
 * @param string|int $num
 * @throws InvalidArgumentException
 * @return string
 */
function bcfact($num)
{
    if (!
filter_var($num, FILTER_VALIDATE_INT) || $num <= 0) {
        throw new
InvalidArgumentException(sprintf('Argument must be natural number, "%s" given.', $num));
    }

    for (
$result = '1'; $num > 0; $num--) {
       
$result = bcmul($result, $num);
    }

    return
$result;
}
?>
George Lund 20-May-2014 09:48
It's worth noting that this library is named very wrongly.

It may be called 'Binary Calculator', but what you're getting is a decimal calculator that can represent base-10 fractions accurately.
ClaudiuS 19-Feb-2013 11:25
Needed to compute some permutations and found the BC extension great but poor on functions, so untill this gets implemented here's the factorial function:

<?php
/* BC FACTORIAL
 * n! = n * (n-1) * (n-2) .. 1 [eg. 5! = 5 * 4 * 3 * 2 * 1 = 120]
 */
function bcfact($n){
   
$factorial=$n;
    while (--
$n>1) $factorial=bcmul($factorial,$n);
    return
$factorial;
}

print
bcfact(50);
//30414093201713378043612608166064768844377641568960512000000000000
?>

数学扩展
PHP Manual