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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 log_base arg, otherwise log() returns the natural logarithm of arg.

arg: The value to calculate the logarithm for
base: The optinal logarithmic base to use (defaults to 'e' and so to the natural logarithm).

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

Version	Description
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: log_b(n) = log(n)/log(b), where log is the neperian (or natural) logarithm.

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