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How can I calculate the value of pi in PHP up to X decimal numbers.
4 decimal points
3.141
64 decimal points
3.141592653589793238462643383279502884197169399375105820974944592
832
There are essentially 3 different methods to calculate pi to many decimals. One of the oldest is to use the power series expansion of atan(x) = x - x^3/3 + x^5/5 - ... together with formulas like pi = 16*atan(1/5) - 4*atan(1/239). This gives about 1.4 decimals per term.
The pi() function in PHP is used to return the value of π . Also, M_PI is a named constant PHP which gives identical value to that of returned by pi() function. It is slightly faster than the pi() function.
php //function to count number of digits function countDigits($MyNum){ $MyNum = (int)$MyNum; if($MyNum != 0) return 1 + countDigits($MyNum/10); else return 0; } $x = 564; $y = 980620; echo "$x contains: ". countDigits($x)." digits\n"; echo "$y contains: ".
Found the source for the broken link @Konamiman posted.
Compared the results to: http://www.angio.net/pi/digits/50.txt and they are the same.
// Source: http://mgccl.com/2007/01/22/php-calculate-pi-revisited
function bcfact($n)
{
return ($n == 0 || $n== 1) ? 1 : bcmul($n,bcfact($n-1));
}
function bcpi($precision)
{
$num = 0;$k = 0;
bcscale($precision+3);
$limit = ($precision+3)/14;
while($k < $limit)
{
$num = bcadd($num, bcdiv(bcmul(bcadd('13591409',bcmul('545140134', $k)),bcmul(bcpow(-1, $k), bcfact(6*$k))),bcmul(bcmul(bcpow('640320',3*$k+1),bcsqrt('640320')), bcmul(bcfact(3*$k), bcpow(bcfact($k),3)))));
++$k;
}
return bcdiv(1,(bcmul(12,($num))),$precision);
}
echo bcpi(1000);
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