# PHP Program to Print Factorial of a Number using for loop

May 2, 2022, Learn eTutorial
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## What is Factorial of a Number?

Factorial of a number is meant by product of all integer numbers from 1 to a given number. The factorial of a positive integer number is denoted by n! (where n is the number). For example, the factorial of number 3 (which is denoted as 3!) is 3 * 2 * 1 is 6. In this program, we are using `for loop` to find the factorial of a number. The factorial of 0 is always 1.

## How to find the factorial of a number in PHP?

To find the factorial of a number in PHP we are using the `for loop`. At first, we accept the integer number from the user and saves it to a variable. Then we should check the number is positive or negative. If the number is negative we should have an error message else continue. Now we can perform the `for loop` till the condition is met and the result is obtained.

## ALGORITHM

Step 1: Read an integer number into the variable num using the PHP function `readline`.

Step 2: Assign the value 1 into the variable fact to store the factorial result.

Step 4: Check the value of num is a positive number using `if` statement. If it is positive perform the following steps otherwise print "Enter a positive number." using `echo`

Step 5: Perform the `for loop` and assign the value of variable fact to variable x and perform the sub-steps until the condition 'fact >= 0' becomes false and decrement the value of variable x in every iteration

(i) 'fact *= x'

Step 6: Print the value of the variable fact as the factorial of the entered number using `echo`

## PHP Source Code

```                                          ```<?php
\$num = (int)readline("Enter the number: "); // read number from user and type casted into integer
\$fact = 1;
if (\$num >= 0) {                             // checking the number is positive or negative
for (\$x = \$num; \$x >= 1; \$x--) {
\$fact *= \$x;                         // multplying the value of fact with x
}
echo "Factorial of \$num is \$fact";
} else {
echo "Enter a positive integer.";
}
?>```
```

## OUTPUT

```Enter the number: 4
Factorial of 4 is 24```

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