Sum of arrays using recursive function

Question

Am a php developer and i have studied about recursive function and i coded to find the sum of elements in an array with recursive function but i got the error.

THE CODE WHICH I GOT FROM INTERNET

$example = array(10,20,30);


function sum_array($array) {


$total = 0;
foreach ($array as $element) {
    if(is_array($element)) {
        $total += sum_array($element);
    } else {
        $total += $element;
    }
}
return $total;


}

echo sum_array($example); // Outputs 60

MY CODE

<?php
 $example = array(10,20,30);

function add_me($arr) {

  if($arr==0) {

    return $arr;



 } 
  return add_me($arr[0]+$arr[1]+$arr[2]);



}

The first code which i found from the internet works well but in case of my code it gives an error. When i called it using echo add_me($example); it forms an error .

Can you please tell me why it is like that ..Any help would be appreciated ..Thanks.

Answer 1

If you're trying to create a recursive function, use the following:

function sum_array($array)
{
    $sum = 0;
    foreach ($array as $value) {
        // if the value itself is an array
        // recurse further: call the function again
        if (is_array($value)) {
            $sum = $sum + sum_array($value);
        }
        // if the value is not an array,
        // simply add it to $sum
        else {
            $sum = $sum + $value;
        }
    }
    return $sum;
}

echo sum_array([3, 4, [5,6], 8]); // => 26

is_array() checks if the value is an array and if so, call the function again. If the value is not an array, the value is simply added to $sum. At the end, $sum is returned.

---

This can be done in multiple ways. Here are some:

Using array_walk_recursive():

function sum_array($array) {
    $sum = 0;
    array_walk_recursive($array, function($v) use (&$sum) {
        $sum += $v;
    });
    return $sum;
}

echo sum_array([3, 4, [5,6], 8]); // => 26

Using array_reduce():

function callback($v, $w) {
    return $v + (is_array($w) ? array_reduce($w, __FUNCTION__) : $w);
}

echo array_reduce([3, 4, [5,6], 8], 'callback'); // => 26

Answer 2

Use array_sum($array) PHP function

Answer 3

Since I can't really do anything with your code to make it functional, I figured I'd explain the function you got from the internet:

//Set sample data
$example = array(10,20,30);
function sum_array($array) {
    //first time called, we start at 0
    $total = 0;
    //Loop through each value in the array
    foreach ($array as $element) {
        //If the value is another array, we use recursion
        if(is_array($element)) {
            //using the recursion, we send the array to this function and add to total
            $total += sum_array($element);
        } else {
            //value was not an array, but scalar, add to total
            $total += $element;
        }
    } // Go to next value
    //Give the total back to asker
    return $total;
}
echo sum_array($example); // Outputs 60

That's the same code you had with comments added for each line. For an example of how it works with the $example array, it would go:

sum_array([10,20,30])
$total = 0
$element = 10
$total += 10  //10
$element = 20
$total += 20 //30
$element = 30
$total += 30 //60

return $total //60

With the example data, no recursion happens at all, it would if you had an array as one of the values, ie [10, [5, 2], 20] and then it would go like:

sum_array([10,[5,2],20])
$total = 0
$element = 10
$total += 10  //10
$element = [5, 2]
sum_array([5,2])
    $total_1 = 0
    $element_1 = 5
    $total_1 += 5 //5
    $element_1 = 2
    $total_1 += 2  //7
    return $total_1 //7
$total += $total_1 //17
$element = 20
$total += 20 //37
return $total //37

Hopefully that will help aid you in understanding recursion.

Answer 4

If you are looking for recursion on arrays, you could use RecursiveArrayIterator class , also see RecursiveIteratorIterator class

A simple illustration (taken from this answer):

<?php
$a = array(1,2,array(3,4, array(5,6,7), 8), 9);
$it = new RecursiveIteratorIterator(new RecursiveArrayIterator($a));
foreach($it as $v) {
    $new_arr[] = $v;
}
echo array_sum($new_arr); // "prints" 45

Answer 5

function sum(array $input) {
    #Base case
    if ( count($input) == 0 ) {
        return;
    }

    if ( is_array( $input[0] ) ) {
        return $input[0][0] + sum( array_merge_recursive( array_slice($input, 1), array_slice($input[0], 1) ) );
    }
    else {
        return $input[0] + sum( array_slice( $input, 1) );    
    }
}

print sum([10, 20, 30]); //60

print sum([10, [10,10], [20,10]]); //60