PHP Numbers Taking Logarithms

PHP Numbers

Taking Logarithms

Problem 

You want to take the logarithm of a number.

Solution

For logs using base e (natural log), use log():

            // $log is about 2.30258
            $log = log(10);

For logs using base 10, use log10():

            // $log10 == 1
            $log10 = log10(10);

For logs using other bases, pass the base as the second argument to log():

            // log base 2 of 10 is about 3.32
            $log2 = log(10, 2);

Discussion

Both log() and log10() are defined only for numbers that are greater than zero. If you pass in a number equal to or less than zero, they return NAN, which stands for not a number.