Error: Notice: Undefined offset: index in ... when sum value same key in a array

Question

$arrOne = array(
    '49' => 5
);

$arrTwo = array(
    '49' => 5
);

$myArray = array($arrOne, $arrTwo);
$sumArray = array();

foreach ($myArray as $k => $subArray) {
    foreach ($subArray as $id => $value) {
        $sumArray[$id] += $value;
    }
}

print_r($sumArray);

Result

error: Notice: Undefined offset: 49 in

how to fix it?

I want result is: array(49 => 10)

@Anant Looks like error messages are disabled there - compare to 3v4l. — Siguza
– Siguza, Commented Jul 1, 2016 at 7:41
a += b is somewhat equivalent to a = a + b. That means you're doing $sumArray[$id] = $sumArray[$id] + $value, when $sumArray[$id] obviously doesn't exist. — deceze
– deceze ♦, Commented Jul 1, 2016 at 7:42
haitruonginfotech please check the answers below and mark+up-vote one as a correct answer. you can up-vote too if they are useful too. thanks. — Death-is-the-real-truth
– Death-is-the-real-truth, Commented Jul 1, 2016 at 23:06

deceze · Accepted Answer · 2016-07-01 07:48:27Z

2

Because it's not defined yet, and you want to add (+=) to an undefined offset. Change the inner code to below:

if (!isset($sumArray[$id])) {
    $sumArray[$id] = $value;
} else {
    $sumArray[$id] += $value;
}

edited Jul 1, 2016 at 7:48

deceze♦

525k89 gold badges806 silver badges954 bronze badges

answered Jul 1, 2016 at 7:44

ashazar

7145 silver badges11 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

ashazar Over a year ago

@deceze, thanks for formatting as code. Somehow it kept giving error.

Siguza · Accepted Answer · 2016-07-01 07:44:07Z

1

Just initialise the index if it doesn't exist yet.

if(!isset($sumArray[$id])) {
    $sumArray[$id] = 0;
}

Patched into your code:

$arrOne = array(
    '49' => 5
);

$arrTwo = array(
    '49' => 5
);

$myArray = array($arrOne, $arrTwo);
$sumArray = array();

foreach ($myArray as $k => $subArray) {
    foreach ($subArray as $id => $value) {
        if(!isset($sumArray[$id])) {
            $sumArray[$id] = 0;
        }
        $sumArray[$id] += $value;
    }
}

print_r($sumArray);

[ Demo ]

answered Jul 1, 2016 at 7:44

Siguza

24.7k6 gold badges58 silver badges105 bronze badges

Collectives™ on Stack Overflow

Error: Notice: Undefined offset: index in ... when sum value same key in a array

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related