(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)
expm1 — 
   Returns exp($num) - 1, computed in a way that is accurate even
   when the value of number is close to zero
  
   expm1() returns the equivalent to
   exp($ computed in a way that is
   accurate even if the value of num) - 1num is near zero,
   a case where exp($ would be
   inaccurate due to subtraction of two numbers that are nearly equal.
  num) - 1
numThe argument to process
   e to the power of num, minus one.
  
