PHP Functions Essential Reference

log

float log(float num) 

Calculates the natural logarithm of a number.

Returns:

Natural logarithm of a number

Description:

Calculates the natural logarithm of the number given by num . log() is the opposite of the exp() function.

Version:

PHP 3, PHP 4

See also:

exp() 
log10() 

Example:

Calculate the natural logarithm of a number

$num = 54.5981; echo "The natural log of $num is ",log($num),"\n";