PHP Exercises: Check whether a number is an Armstrong number or not

PHP: Exercise-32 with Solution

Write a PHP program to check whether a number is an Armstrong number or not. Return true if the number is Armstrong otherwise return false.

An Armstrong number of three digits is an integer so that the sum of the cubes of its digits is equal to the number itself. For example, 153 is an Armstrong number since 1**3 + 5**3 + 3**3 = 153

Sample Solution:

PHP Code:

<?php
// Function to check if a number is an Armstrong number
function armstrong_number($num) {
  // Calculate the length of the number
  $sl = strlen($num);
  
  // Initialize a variable to store the sum of digits raised to the power of length
  $sum = 0;
  
  // Convert the number to a string for individual digit access
  $num = (string)$num;
  
  // Iterate over each digit of the number
  for ($i = 0; $i < $sl; $i++) {
    // Add the current digit raised to the power of length to the sum
    $sum = $sum + pow((string)$num{$i}, $sl);
  }
  
  // Check if the sum is equal to the original number
  if ((string)$sum == (string)$num) {
    return "True";
  } else {
    return "False";
  }
}

// Test cases
echo "Is 153 Armstrong number? " . armstrong_number(153);
echo "\nIs 21 Armstrong number? " . armstrong_number(21);
echo "\nIs 4587 Armstrong number? " . armstrong_number(4587) . "\n";

?>

Sample Output:

Is 153 Armstrong number? True                                          
Is 21 Armstrong number? False                                          
Is 4587 Armstrong number? False 

Flowchart:

PHP Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Write a PHP program to swap two variables.
Next: Write a PHP program to convert word to digit.