(PHP 4 >= 4.1.0, PHP 5, PHP 7)
log1p — Returns log(1 + number), computed in a way that is accurate even when the value of number is close to zero
log1p ( float $number ) : float
log1p() returns log(1 + number) computed in a way that is accurate even when the value of number is close to zero. log() might only return log(1) in this case due to lack of precision.
number
The argument to process
log(1 + number)
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https://www.php.net/manual/en/function.log1p.php