PHP Manual: log

function log(float $num, float $base = M_E): float

If the optional base parameter is specified, log() returns log_base num, otherwise log() returns the natural logarithm of num.

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

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

Throws a ValueError if base is less than or equal to 0.

Version	Description
8.0.0	Now throws a ValueError if `base` is less than or equal to `0`. Previously, an `E_WARNING` was raised and `false` was returned.

log