Recursion is used for multiplying an integer number by all numbers with inferior values.Factorial and Euler Constant calculation can also calculate the Euler or Napier constant (e = 2,71...) with up to 15 iterations.Requirements: PHP 3.0 or higher

The factorial of a given positive integer number can be calculated.Key Features of Simple Math:- Calculate the number of all possible permutations of a subset of elements of a given size without repeating elements- Calculate the number of all possible combinations of a subset of elements of a given size without considering the order or repeating elementsRequirements:PHP 5.0 or higher