PHP Exercises: Compute the sum of the digits of a number

Last update on May 26 2025 13:16:36 (UTC/GMT +8 hours)

45. Sum of Digits

Write a PHP program to compute the sum of the digits of a number.

Sample Solution:

PHP Code:

<?php
// Define a function to calculate the sum of digits in a given number
function sum_of_digits($nums) {
    // Initialize a variable to store the sum of digits
    $digits_sum = 0;

    // Iterate through each digit in the number
    for ($i = 0; $i < strlen($nums); $i++) {
        // Add the current digit to the sum
        $digits_sum += $nums[$i];
    }

    // Return the sum of digits
    return $digits_sum;
}

// Test the function with example numbers
echo sum_of_digits("12345")."\n";
echo sum_of_digits("9999")."\n";

?>

Explanation:

Function Definition:

The function sum_of_digits($nums) is defined to calculate the sum of the digits of a given number passed as a string.

Initialize Sum Variable:

A variable $digits_sum is initialized to 0 to hold the cumulative sum of the digits.

Iterate Through Digits:

A for loop iterates through each character in the string $nums using the length of the string (strlen($nums)) as the loop's limit.
The loop variable $i represents the current index of the character being processed.

Add Each Digit:

Inside the loop, the current digit (as a character) is accessed using $nums[$i] and added to the $digits_sum variable.
Since the digits are passed as a string, PHP automatically converts the character to its integer value when performing the addition.

Return the Result:

After the loop completes, the function returns the total sum of the digits.

Test Cases:

The function is tested with two example inputs:

sum_of_digits("12345"), which calculates 1 + 2 + 3 + 4 + 5, resulting in 15.
sum_of_digits("9999"), which calculates 9 + 9 + 9 + 9, resulting in 36.

The results are printed to the output.

Output:

15                                                          
36

Flowchart:

For more Practice: Solve these Related Problems:

Write a PHP script to compute the sum of digits of a number using a recursive approach.
Write a PHP script to calculate the sum of digits for very large numbers represented as strings.
Write a PHP script that iterates over each digit of an integer and accumulates the total using a while loop.
Write a PHP function to sum digits and verify correctness across multiple test cases.

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PHP Code Editor:

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