CODEWITHSUNDEEP
phparraysforeach
Ac0
Ac0

Reputation: 51

Add previous value on array - PHP

I'm trying to figure out how to make an array add the value of the previous array, so far, looking at the PHP manual I got how to add a single value for each position of the array, but I don't understand how can I add the previous value to the actual value. That's what i got checking the manual:

<!DOCTYPE html>
<head>
</head>
    <body>
        <?php
           foreach (array(422, 322, -52323, 7452) as &$val) {
            $val = $val + 2;
            
                echo "$val<br>";

           }
        ?>
    </body>

I know that I have to change the "+ 2" with "add previous value" but don't know how I can tell it to do that, tried to add "$val[0]" or "$val[$i]" but not doing what I think it does.

Thank you!

Upvotes: 0

Views: 1148

Answers (2)

The fourth bird
The fourth bird

Reputation: 163287

You are directly iterating over an array, and in that case you don't need the reference to &$val, you can just use $val

If you don't want to store the array in a variable, you could also "remember" the previous value of the iteration (which will also work in case the keys are not numerical for example)

$previous = null;
foreach (array(422, 322, -52323, 7452) as $val) {
    if ($previous) {
        $previous += $val;
    } else {
        $previous = $val;
    }
    echo $previous . PHP_EOL;
}

Output

422
744
-51579
-44127

See a Php demo.

Upvotes: 0

rickdenhaan
rickdenhaan

Reputation: 11318

You've complicated matters by putting the array directly into foreach. To get the previous value, you need to have access to the array itself.

Once you have that, you can get the index of the current value with foreach, which you can use to determine the index of the previous value:

$array = array(422, 322, -52323, 7452);
foreach ($array as $index => &$val) {
    // the first index is 0, in that case there is no previous value
    // (trying to access $array[$index - 1] ($array[-1]) will fail then)
    if ($index > 0) {
        $val = $val + $array[$index - 1];
    }

    echo "$val<br>";
}

Upvotes: 5

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