PHP Numbers Calculating Exponents

PHP Numbers

Calculating Exponents

Problem

You want to raise a number to a power.

Solution

To raise e to a power, use exp():

            // $exp (e squared) is about 7.389
            $exp = exp(2);

To raise it to any power, use pow():

            // $exp (2^e) is about 6.58
            $exp = pow( 2, M_E);
            // $pow1 (2^10) is 1024
            $pow1 = pow( 2, 10);
            // $pow2 (2^-2) is 0.25
            $pow2 = pow( 2, -2);
            // $pow3 (2^2.5) is about 5.656
            $pow3 = pow( 2, 2.5);
            // $pow4 ( (-2)^10 ) is 1024
            $pow4 = pow(-2, 10);
            // is_nan($pow5) returns true, because
            // fractional exponent of negative 2 is not a real number.
            $pow5 = pow(-2, -2.5);

Discussion

The built-in constant M_E is an approximation of the value of e. It equals 2.7182818284590452354. So exp($n) and pow(M_E, $n) are identical.

It’s easy to create very large numbers using exp() and pow(); if you outgrow PHP’s maximum size (almost 1.8e308).  With exp() and pow(), PHP returns INF (infinity) if the result is too large and NAN (not a number) on an error.