(PHP 4, PHP 5, PHP 7)
Natural logarithm
float log ( float $arg [, float $base = M_E ] )
If the optional base parameter is specified, log() returns logbasearg, otherwise log() returns the natural logarithm of arg.
Parameters:
arg
The value to calculate the logarithm for
base
The optional logarithmic base to use (defaults to 'e' and so t