The factorial of a number is the product of all integers up to and including that number, so the factorial of 5 is 120.

Example

```
4! = 4*3*2*1 = 24
5! = 5*4*3*2*1 = 120
```

## Points to be noted.

- It is denoted by
**n!**and is calculated only for positive integers. **Factorial of 0**is always**1**- The simplest way to find the factorial of a number is by using a
**loop**or Using**recursive method**

**factorial program in php using for loop**

```
<?php
$num = 5;
$fact = 1;
for($i = 1; $i <=$num;$i++) // initially, i = 1
{
$fact = $fact * $i; //
}
echo "factorial of $num is = ".$fact;
?>
```

**Note **: **Above code will be iterate : 1 * 2* 3* 4* 5 = 120**

**Factorial in PHP**

```
<?php
$num = 7;
$fact = 1;
for($i = $num; $i >= 1; $i--) // intiallly, i = 7
{
$fact = $fact * $i; //
}
echo "factorial of $num is = ".$fact;
?>
```

**Note **: **Above code will be iterate : 7*6*5 * 4* 3* 2* 1 = 5040**

## factorial program in php using recursion | factorial recursion

```
<?php
function getFactorialofNumber($number){
if($number <= 1){
return 1;
}
else{
return $number * getFactorialofNumber($number - 1);
}
}
echo "factorial of 6 is = ".getFactorialofNumber(6);
?>
```