PHP Factorial Program

by Online Tutorials Library July 22, 2022

Factorial Program

The factorial of a number n is defined by the product of all the digits from 1 to n (including 1 and n).

For example,

Note:

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.

There are two ways to find factorial in PHP:

Using loop
Using recursive method

Logic:

Take a number.
Take the descending positive integers.
Multiply them.

Factorial in PHP

Factorial of 4 using for loop is shown below.

Example:

  <?php  $num = 4;  $factorial = 1;  for ($x=$num; $x>=1; $x–)   {    $factorial = $factorial * $x;  }  echo “Factorial of $num is $factorial”;  ?>  

Output:

Factorial using Form in PHP

Below program shows a form through which you can calculate factorial of any number.

Example:

  <html>  <head>  <title>Factorial Program using loop in PHP</title>  </head>  <body>  <form method=”post”>  Enter the Number:<br>  <input type=”number” name=”number” id=”number”>  <input type=”submit” name=”submit” value=”Submit” />  </form>  <?php   if($_POST){  $fact = 1;  //getting value from input text box ‘number’  $number = $_POST[‘number’];  echo “Factorial of $number:<br><br>”;  //start loop  for ($i = 1; $i <= $number; $i++){  $fact = $fact * $i;  }  echo $fact . “<br>”;  }  ?>  </body>  </html>  

Output:

Factorial using Recursion in PHP

Factorial of 6 using recursion method is shown.

Example:

  <?php  function fact ($n)  {      if($n <= 1)       {          return 1;      }      else       {          return $n * fact($n – 1);      }  }    echo “Factorial of 6 is ” .fact(6);  ?>  

Output:

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