Group and sum 2d array data into a flat associative array

Question

I am trying to parse an array of strings with irrelevant leading text (to be removed) then create an associative array where values are summed if the same key is encountered more than once.

$assessmentArr = [
    'a_b_money-rewards=30',
    'c_d_status-stability=15',
    'e_f_personal-professional-development=32',
    'g_h_community-support=9',
    'i_j_money-rewards=12',
    'k_l_status-stability=16',
    'm_n_personal-professional-development=29',
];

foreach($assessmentArr as $data) {
    $fullArr = explode("_", $data);
    $resultArr = explode("=", $fullArr[2]);
    // what do I do with $resultArr?
}

Desired result:

Array
(
    [community-support] => 33
    [money-rewards] => 42
    [status-stability] => 31
    [personal-professional-development] => 61
)

I found this question: How to merge two arrays by summing the merged values which will assist me in merging and adding the values together, but I'm not sure how to go about it when the arrays aren't assigned to a variable. Is what I am trying to do possible or am I going about this the wrong way?

can you tell in your desired output how you decide values. because it's not matched to the array what you are getting right now? — Alive to die - Anant, Jun 03 '15 at 19:51
[Group array data on one column and sum data from another column](https://stackoverflow.com/q/3286749/2943403) — mickmackusa, Mar 16 '23 at 10:50

score 2 · Accepted Answer · answered Jun 03 '15 at 19:52

Don't make it complicated, just check if the results array already has an element with that key and if not initialize it otherwise add it. E.g.

(Add this code in your loop):

if(!isset($result[$resultArr[0]]))
    $result[$resultArr[0]] = $resultArr[1];
else
    $result[$resultArr[0]] += $resultArr[1];

Then you have your desired array:

print_r($result);

score 0 · Answer 2 · answered Jun 03 '15 at 20:00

You could do it like this

$assessmentArr = explode("&", $assessmentData);
$finalArr = array();
foreach($assessmentArr as $data) {
    $fullArr = explode("_", $data);

    // Break down to only archetype and value
    $resultArr = explode("=", $fullArr[2]);
    if(array_key_exists($resultArr[1], $finalArr)){
        $finalArr[$resultArr[0]] += $resultArr[1];
    }else{
        $finalArr[$resultArr[0]] = $resultArr[1];
    }
}

First check, if the key already exists in the array, if so you add the value to the value in the final array. Otherwise you add the new index to the final array, with the value from resultArr as inital value.

... way too slow :/

score 0 · Answer 3 · answered Mar 16 '23 at 10:31

Upon parsing the text into its meaningful parts, use the hyphenated strings as keys and the numbers as values. If a key is encountered for the first time, store the sum of 0 and the current value; otherwise sum and store the stored value and the current value.

Code: (Demo)

$result = [];
foreach (explode("&", $assessmentData) as $data) {
    sscanf(preg_replace('/.*_/', '', $data), '%[^=]=%d', $k, $v);
    $result[$k] = ($result[$k] ?? 0) + $v;
}
var_export($result);

Or for more direct parsing, use a preg_match_all() call. Demo

$result = [];
preg_match_all('/[^_]*_[^_]*_([^=]+)=(\d+)/', $assessmentData, $matches, PREG_SET_ORDER);
foreach ($matches as $m) {
    $result[$m[1]] = ($result[$m[1]] ?? 0) + $m[2];
}
var_export($result);

Group and sum 2d array data into a flat associative array

3 Answers3

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