Factorial Program in PHP
Factorial of a number is the product of all numbers starting from 1 up to the number itself. While calculating the product of all the numbers, the number is itself included.
Factorial of a number is calculated
for positive integers only. The factorial of 0 is always 1 and the factorial of
a negative number does not exist. It is denoted by ‘!’ preceded by the number.
Example n! where n is the number
So,
Factorial of 5! means factorial of 5
Factorial of 7! means factorial of 7
For example, the factorial of number
5 is:
5! =5*4*3*2*1 = 120
Similarly, the factorial of number 7
is:
7! = 7*6*5*4*3*2*1 = 5040
and so on..
Now how do we actually find the
factorial, we can do it using
- for
loop (without recursion)
- with
recursion
Factorial Logic
The logic behind getting the
factorial of the number is as per the following.
- Get
the number whose factorial is to be calculated.
- Get
all the numbers starting from 1 up to that number.
- Get
the multiplication of all the numbers.
Remember the factorial of 0! = 1.
fact.php -program name
<?php
//example to calculate factorial of a number using simple for loop
//declaring the input number as 5
$input=5;
//declaring the fact variable as 1
$fact =1;
//iterating using for loop
for($i=$input; $i>=1;$i--) {
// multiply each number up to 5 by its previous consecutive number
$fact = $fact * $i;
}
// Print output of the program
echo '<br>'. 'The factorial of the number 5 is '. $fact
?>
Example :2
In the below program,
we have used a simple HTML form with an
input text and a submit button. The input box is used to get user input. The
submit button is used to submit the form data. Followed by that is the PHP code
to iterate for loop wherein all the logic is present, which we learned in the previous
program. So now the same logic is used with an input form.
If
the user inputs a positive number through the input box in the form, the
factorial of that number is calculated and the result is printed.
facto.php-program name
<html>
<head>
<title> Factorial Program</title>
</head>
<body>
<form method="POST">
<label>Enter a number</label>
<input type="text" name="number" />
<input type="submit" name="submit" value="Submit" />
</form>
<?php
// example to demonstrate factorial of a number using form
if($_POST) {
$input = $_POST['number'];
$fact=1;
//iterating using for loop
for($i=$input; $i>=1;$i--) {
$fact = $fact * $i;
}
// Print output of the program
echo '<br>'. 'The factorial of the number '.$input.' is ' . $fact;
}
?>
</body>
</html>
Example:3
We know that recursion is calling a
function within a function. In the following example, we will use recursion and
find the factorial of the number using PHP code. The main logic is wrapped in a function
name Factorial_Function. Within this function if the input is greater that one,
then the same function is called again and if the input is less than or equal
to 1 then one is returned.
<?php
//Example to demonstrate factorial of a number using recursion
//function containing logic of factorial
function Factorial_Function($input)
{
// if the input is less than or equal to 1 then return
if($input <=1) {
return 1;
}
// else do a recursive call and continue to find the factorial
return $input * Factorial_Function($input-1); //doing a recursive call
}
echo "Factorial of 9 is ".Factorial_Function(9);
?>
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