Math
PHP Manual

log

(PHP 4, PHP 5)

log — Natural logarithm

Описание

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 .

Список параметров

arg

The value to calculate the logarithm for

base

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

Возвращаемые значения

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

Список изменений

Версия Описание
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.

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Math
PHP Manual