PHP log() Function: Natural Logarithm with Optional Base

The PHP log() function returns the natural logarithm of a given number, or the logarithm with an optional base if the base argument is provided.

Signature: float log(float $arg [, float $base = M_E]) Parameters:

arg : the value whose logarithm is to be calculated.

base (optional): the logarithmic base; defaults to the mathematical constant e, yielding the natural logarithm.

Return value: the logarithm of arg with respect to base, or the natural logarithm if base is omitted.

Example usage:

<?php
echo log(2.7183)."<br>";
echo log(2)."<br>";
echo log(1)."<br>";
echo log(0);
?>

Resulting output:

1.000006684914
0.69314718055995
0
-INF