# PHP Program - Find Factorial of a Number

The factorial of a positive integer is the multiplication of all positive integer less than or equal to that number.

factorial of number n = n! = n(n-1)(n-2)...1

### For Example:

5! = 5 × 4 × 3 × 2 × 1 = 120

4! = 4 × 3 × 2 × 1 = 24

### Method 1: Using Recursive method

In the example below, a recursive function called factorial() is used to calculate factorial of a number.

```<?php
function factorial(\$x) {
if (\$x == 0 || \$x == 1)
return 1;
else
return \$x*factorial(\$x-1);
}

echo "10! =  ".factorial(10)."\n";
echo "6! =  ".factorial(6)."\n";
?>
```

The above code will give the following output:

```10! =  3628800
6! =  720
```

### Method 2: Using Iterative method

The factorial of a number can also be calculated using iterative method.

```<?php
function factorial(\$x) {
\$finalnum = 1;
for(\$i = \$x; \$i > 0; \$i--) {
\$finalnum = \$finalnum * \$i;
}
return \$finalnum;
}

echo "10! =  ".factorial(10)."\n";
echo "6! =  ".factorial(6)."\n";
?>
```

The above code will give the following output:

```10! =  3628800
6! =  720
```

### Method 3: Using Ternary Operator

In the example below, the factorial of a number is calculated using ternary operator.

```<?php
function factorial(\$x) {
\$y = (\$x == 0 || \$x == 1)? 1 : \$x*factorial(\$x-1);
return \$y;
}

echo "10! =  ".factorial(10)."\n";
echo "6! =  ".factorial(6)."\n";
?>
```

The above code will give the following output:

```10! =  3628800
6! =  720
```

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