(PHP 4 >= 4.0.7, PHP 5)
expm1 вЂ” Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zero
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(arg ) - 1' computed in a way that is accurate even if the value of arg is near zero, a case where 'exp (arg ) - 1' would be inaccurate due to subtraction of two numbers that are nearly equal.
Note: This function is not implemented on Windows platforms.
The argument to process
'e' to the power of arg minus one