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.

It must be if($arr==0) { . You don't have $array defined anywhere , so why use it ? This solves just the syntactical problem issue.. — Shankar Narayana Damodaran
– Shankar Narayana Damodaran, Commented Apr 19, 2014 at 6:32

Amal · Accepted Answer · 2014-04-19 09:03:50Z

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

PravinS · Accepted Answer · 2014-04-19 06:34:20Z

1

Use array_sum($array) PHP function

answered Apr 19, 2014 at 6:34

PravinS

2,5943 gold badges22 silver badges27 bronze badges

2 Comments

user3550798 Over a year ago

yes i know ..and i did it to learn about recrusion method in php

PravinS Over a year ago

@user3550798 - factorial is good example to learn recursive method :)

Jon · Accepted Answer · 2014-04-19 06:53:12Z

1

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.

answered Apr 19, 2014 at 6:53

Jon

4,7362 gold badges27 silver badges37 bronze badges

3 Comments

user3550798 Over a year ago

so in the line "$total += sum_array($element);" the whole array elements are added to $total ...right ?

Jon Over a year ago

The whole inner-array. In my expanded example, that would be the [5, 2]

Amal Over a year ago

@user3550798: $foo += $bar is a shorter way of writing $foo = $foo + $bar. In this case, it means $total = $total + sum_array($element) (where $element is [5, 2]).

Community · Accepted Answer · 2023-11-21 15:10:29Z

0

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

edited Nov 21, 2023 at 15:10

CommunityBot

11 silver badge

answered Apr 19, 2014 at 6:43

Shankar Narayana Damodaran

68.6k43 gold badges102 silver badges129 bronze badges

4 Comments

Amal Over a year ago

Just a note: You don't need to call array_sum() again. See this answer.

Shankar Narayana Damodaran Over a year ago

@AmalMurali, Come on I know that. The $a array is actually flattened to $new_arr so that the OP can use it for other purposes too. ;)

Amal Over a year ago

I'm sure you know that. But I thought the OP wasn't really familiar with recursion, so that was more of an FYI comment.

Shankar Narayana Damodaran Over a year ago

@AmalMurali, I intentionally did that , since after sometime OP may come and ask how to add the first four elements , last four elements , third and seventh element.. as such. So putting it inside an array would be more easier. Also, since OP is familiar with array_sum() , I used that.

slier · Accepted Answer · 2017-02-02 04:13:06Z

0

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

edited Feb 2, 2017 at 4:13

answered Feb 1, 2017 at 8:32

slier

6,6566 gold badges41 silver badges58 bronze badges

1 Comment

Ferrybig Over a year ago

While this code snippet may solve the question, including an explanation really helps to improve the quality of your post. Remember that you are answering the question for readers in the future, and those people might not know the reasons for your code suggestion. - From review

Collectives™ on Stack Overflow

Sum of arrays using recursive function

THE CODE WHICH I GOT FROM INTERNET

MY CODE

5 Answers 5

Comments

2 Comments

3 Comments

4 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

THE CODE WHICH I GOT FROM INTERNET

MY CODE

5 Answers 5

Comments

2 Comments

3 Comments

4 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related