PHP Class Exercises : Calculate the factorial of an integer

PHP class: Exercise-3 with Solution

Write a PHP class that calculates the factorial of an integer.

Sample Solution:

PHP Code:

<?php
// Define a class named factorial_of_a_number
class factorial_of_a_number
{
    // Declare a protected property named $_n
    protected $_n;

    // Define the constructor method which accepts a parameter $n
    public function __construct($n)
    {
        // Check if the parameter $n is not an integer
        if (!is_int($n)) {
            // Throw an exception if $n is not an integer
            throw new InvalidArgumentException('Not a number or missing argument');
        }
        // Assign the value of $n to the protected property $_n
        $this->_n = $n;
    }

    // Define a method named result to calculate the factorial of the number
    public function result()
    {
        // Initialize the factorial variable to 1
        $factorial = 1;
        // Iterate from 1 to the value of $_n
        for ($i = 1; $i <= $this->_n; $i++) {
            // Multiply the factorial by the current value of $i
            $factorial *= $i;
        }
        // Return the calculated factorial
        return $factorial;
    }
}

// Create an instance of the factorial_of_a_number class with the argument 5
$newfactorial = new factorial_of_a_number(5);

// Call the result method of the $newfactorial object and output the result
echo $newfactorial->result();
?>

Output:

120

Explanation:

In the exercise above,

• class factorial_of_a_number {: This line defines a class named "factorial_of_a_number".
• protected $_n;: This line declares a protected property named '$_n' to store the number for which the factorial will be calculated.
• public function __construct($n) {: This line defines the constructor method of the class which accepts a parameter '$n'.
• if (!is_int($n)) {: This line checks if the provided argument '$n' is not an integer using the is_int function.
• throw new InvalidArgumentException('Not a number or missing argument');: If the argument '$n' is not an integer, an "InvalidArgumentException" is thrown with the specified message.
• $this->_n = $n;: This line assigns the value of the parameter '$n' to the protected property '$_n'.
• public function result() {: This line defines a public method named "result()" which calculates the factorial of the number stored in '$_n'.
• for ($i = 1; $i <= $this->_n; $i++) {: This line initializes a for loop to iterate from 1 to the value of '$_n' and calculates the factorial.
• return $factorial;: This line returns the calculated factorial value.
• $newfactorial = new factorial_of_a_number(5);: This line creates a new instance of the "factorial_of_a_number" class with the argument 5.
• echo $newfactorial->result();: This line calls the "result()" method of the "$newfactorial" object and outputs the calculated factorial value.

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