Factorial of a number using for loop and recursive functions in PHP

Current factorial example

The factorial of a non-negative integer is the product of every positive integer up to that number. By definition, 0! is 1.

<?php
$number = 5;
$factorial = 1;

for ($i = 2; $i <= $number; $i++) {
    $factorial *= $i;
}

echo $number . '! = ' . $factorial;
?>

For form input, validate that the value is an integer and reject negative numbers before calculating the factorial.

Factorial of a number is product of all integers from 1 up to the number ( inclusive ).
Factorial of 5 is 1*2*3*4*5 = 120
Or
n! = 1*2*3â€¦.n

Factorial using looping

$n1=50; // change this number
for($i=1;$i<=($n1/2); $i++){
	if($n1%$i == 0 )
		echo " $i," ;
}
echo  $n1 ;

Factorial of an input number through sticky form in PHP using for loop or using recursive function

Using for loop

More details on for loop in PHP.

$n1=5; // change this number 
$factorial=1;
for ($i=1; $i<=$n1;$i++){
	$factorial=$factorial*$i;
}
echo "Factorial of $n1 : $factorial";

Output

Factorial of 5 : 120

Asking user input

We can use one sticky form to take user input and calculate the factorial of input number.

$n1=$_POST['n1'] ?? '';
echo "<form method=POST action=''>
<input type=text name=n1 value='$n1'> 
<input type=submit value=Submit>
</form>";
$factorial=1;
for ($i=1; $i<=$n1;$i++){
	$factorial=$factorial*$i;
}

echo "Factorial of $n1 : $factorial";

Factorial of a number by using recursive function

By using recursive function we can call the function itself from within the function.

function fact($n){
if($n<>1){	
$factorial = $n * fact($n-1);
return $factorial;
}else{
return 1;		
}
}
echo "Factorial of 6 : ".fact(6);

Output is here

Factorial of 6 : 720

Introduction to PHP Sum of digits of a number Strong Number
Armstrong number Fibonacci Series
Basic Codes Check the string or number is Palindrome or not in PHP

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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Factorial of a Number using PHP