PHP expm1 function

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expm1

(PHP 4 >= 4.1.0, PHP 5)

expm1 —
Returns exp(number) – 1, computed in a way that is accurate even
when the value of number is close to zero
Descriptionfloat expm1 ( float number )

Warning

This function is
EXPERIMENTAL. The behaviour of this function, the
name of this function, and anything else documented about this
function may change without notice in a future release of PHP.
Use this function at your own risk.

expm1() returns the equivalent to
‘exp(number) – 1′ computed in a way that is
accurate even if the value of number is near zero,
a case where ‘exp (number) – 1′ would be
inaccurate due to subtraction of two numbers that are nearly equal.

Note: This function is not
implemented on Windows platforms.

See also log1p() and
exp().