π (pi) is a mathematical constant whose value is the ratio of any Euclidean plane circle's circumference to its diameter; this is the same value as the ratio of a circle's area to the square of its radius.
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
php math pi