PHP Manual


(PHP 4 >= 4.0.7, PHP 5)

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


float expm1 ( float $arg )

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

Return Values

'e' to the power of arg minus one

See Also

PHP Manual