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PHP log() Function

Complete PHP Math Reference

Definition and Usage

The log() function returns the natural logarithm (base E) of a number.

Syntax

log(x,base)

Parameter	Description
x	Required. A number
base	Optional. If the base parameter is specified, log() returns log_base x. Note: The base parameter became available in PHP 4.

Tips and Notes

Note: If the parameter x is negative, -1.#IND is returned.

Example

In the following example we will use the log() function on different numbers:

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

The output of the code above will be:

1.00000668491
0.69314718056
0
-1.#INF
-1.#IND