PHP Manual: log


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log

(PHP 3, PHP 4, PHP 5)

log -- Natural logarithm

Description

float log ( float arg [, float base] )

If the optional base parameter is specified, log() returns logbase arg, otherwise log() returns the natural logarithm of arg.

Parameters

arg

The value to calculate the logarithm for

base

The optinal logarithmic base to use (defaults to 'e' and so to the natural logarithm).

Return Values

The logarithm of arg to base, if given, or the natural logarithm.

ChangeLog

VersionDescription
Since 4.3.0 The optinal 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.

See Also

log10()
exp()
pow()

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