php man page for gmp_fact

GMP_FACT(3)								 1							       GMP_FACT(3)

gmp_fact - Factorial

SYNOPSIS
       GMP gmp_fact (mixed  $a)

DESCRIPTION
	Calculates factorial ( a!) of $a.

PARAMETERS
	      o $a
		-  The	factorial  number.  Either  a  GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric
		string provided that it is possible to convert the latter to a number.

RETURN VALUES
	A GMP number resource in PHP 5.5 and earlier, or a GMP object in PHP 5.6 and later.

EXAMPLES
       Example #1

	      gmp_fact(3) example

	      <?php
	      $fact1 = gmp_fact(5); // 5 * 4 * 3 * 2 * 1
	      echo gmp_strval($fact1) . "
";

	      $fact2 = gmp_fact(50); // 50 * 49 * 48, ... etc
	      echo gmp_strval($fact2) . "
";
	      ?>

	      The above example will output:

	      120
	      30414093201713378043612608166064768844377641568960512000000000000

PHP Documentation Group 													       GMP_FACT(3)