PHP Software Source Code Math Library Integer Factorial Equation

AJ PHP Software Source Code Math Library
Factorial Integer

integer factorial_integer ( integer n)

Description:

factorial_integer returns the the factorial given an integer.

Source Code:

function factorial_integer ($k)
{
//variable and initializations
$the_result = 1;

  //check to see if k is an integer
  if (!is_int($k))
  {
    return "error";
  }

  //check for k < 0
  if ($k < 0)
  {
    return "error";
  }

  //0! = 1
  if ($k == 0)
  {
    return 1;
  }

  //calculate the result
  for ($i = 2; $i <= $k; $i++)
  {
    $the_result = $the_result * $i;
  }

//return the value
return $the_result;
}

Example:

<?
include ("ajmath.php");

$n = 5;

$the_factorial = factorial_integer($n);

echo "n = $n<br>";
echo "the_factorial = $the_factorial<br>";
?>

array average	solve for the average of an array
factorial integer	solve for the factorial of an integer
log base	solve for the base of the logarithm function

References - Books:

Max A. Sobel, Nobert Lerner. 1991. Precalculus Mathematics. Prentice Hall.