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

Last update on May 30 2022 11:45:40 (UTC/GMT +8 hours)

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 armstrong_number($num) {
  $sl = strlen($num);
  $sum = 0;
  $num = (string)$num;
  for ($i = 0; $i < $sl; $i++) {
    $sum = $sum + pow((string)$num{$i},$sl);
  }
  if ((string)$sum == (string)$num) {
    return "True";
  } else {
    return "False";
  }
}
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:

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PHP: Tips of the Day

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC