PHP | Factorial of a number

We already know how to get the factorial of a number in other languages. Let’s see how this is done in PHP using both recursive and non-recursive ways. Examples:

Input : 5
Output : 120

Input : 10
Output : 3628800

Method 1: Iterative way In this method, we simply used the for loop to iterate over the sequence of numbers to get the factorial. 

PHP

<?php
// PHP code to get the factorial of a number
// function to get factorial in iterative way
function Factorial($number){
    $factorial = 1;
    for ($i = 1; $i <= $number; $i++){
    $factorial = $factorial * $i;
    }
    return $factorial;
}

// Driver Code
$number = 10;
$fact = Factorial($number);
echo "Factorial = $fact";
?>

Output:

3628800

Time Complexity: O(N) where N is the number of which factorial is being calculated

Auxiliary Space: O(1)

Method 2: Use of recursion In this method we are calling the same method to get the sequence of the factorial. 

PHP

<?php
// PHP code to get the factorial of a number
// function to get factorial in iterative way
function Factorial($number){
    if($number <= 1){
        return 1;
    }
    else{
        return $number * Factorial($number - 1);
    }
}

// Driver Code
$number = 10;
$fact = Factorial($number);
echo "Factorial = $fact";
?>

Output:

3628800

Time Complexity: O(N) where N is the number of which factorial is being calculated

Auxiliary Space: O(N)