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Natural logarithm log
(PHP 4, PHP 5)
log — Natural logarithm
Description
float log ( float$arg
[, float$base
= M_E ] )If the optional
base
parameter is specified, log() returns logbasearg
, otherwise log() returns the natural logarithm ofarg
.Parameters
arg
The value to calculate the logarithm for
base
The optional logarithmic base to use (defaults to 'e' and so to the natural logarithm).
Return Values
The logarithm of
arg
tobase
, if given, or the natural logarithm.Changelog
Version Description 4.3.0 The optional parameter base
became available. For older versions you can calculate the logarithm in base b of a number n, but using the mathematical identity: logb(n) = log(n)/log(b), where log is the neperian (or natural) logarithm.