PHP | Sum of digits of a number

This is a simple PHP program where we need to calculate the sum of all digits of a number.
Examples:

Input : 711 
Output : 9

Input : 14785
Output : 25

In this program, we will try to accept a number in the form of a string and then iterate through the length of the string. While iterating we will extract the digit from each position and then add them to the previously extracted digit, thus getting the sum.

<?php
// PHP program to calculate the sum of digits
function sum($num) {
    $sum = 0;
    for ($i = 0; $i < strlen($num); $i++){
        $sum += $num[$i];
    }
    return $sum;
}

// Driver Code
$num = "711";
echo sum($num);
?>

Output:

9