PHP program to sum the digits in a number

To sum the digits in a number, we can treat the number as a string and iterate through each character, converting it back to an integer and adding to our sum.

Example

<?php
   function sum_of_digits($my_num){
      $sum = 0;
      for ($i = 0; $i < strlen($my_num); $i++){
         $sum += $my_num[$i];
      }
      return $sum;
   }
   $my_num = "65";
   print_r("The sum of digits is ");
   echo sum_of_digits($my_num);
?>

Output

The sum of digits is 11

How It Works

The function sum_of_digits takes a number as a parameter. It initializes a variable $sum to 0, then iterates through each character of the number using strlen() to get the length. Each character is automatically converted to an integer when added to the sum.

For the number "65", the function processes:

• First digit: 6 (adds 6 to sum)
• Second digit: 5 (adds 5 to sum)
• Total sum: 6 + 5 = 11

Alternative Method Using Mathematical Approach

<?php
   function sum_of_digits_math($num){
      $sum = 0;
      while ($num > 0) {
         $sum += $num % 10;
         $num = intval($num / 10);
      }
      return $sum;
   }
   $number = 65;
   echo "The sum of digits is " . sum_of_digits_math($number);
?>

The sum of digits is 11

Conclusion

Both methods effectively sum the digits of a number. The string approach is simpler to understand, while the mathematical method using modulo and division operations is more traditional in programming.