Filter out differences between correlated data sets from two multidimensional arrays

Question

I have 2 arrays:

$big_array = [
    [
        ['correct' => FALSE, 'answer' => 'false answer1'],
        ['correct' => FALSE, 'answer' => 'false answer2'],
        ['correct' => FALSE, 'answer' => 'false answer3'],
        ['correct' => TRUE, 'answer' => 'correct answer'],
    ]
];

$small_array = [
    [
        ['correct' => FALSE, 'answer' => 'false answer1'],
    ]
];

I want to make array_diff($big_array, $small_array) but it's not working how I want it to.

Currently, it gives me an empty array as a result, where I want the outcome to be:

$outcome_array = [
    [
        ['correct' => FALSE, 'answer' => 'false answer2'],
        ['correct' => FALSE, 'answer' => 'false answer3'],
        ['correct' => TRUE, 'answer' => 'correct answer'],
    ]
];

first suggestion : post the code that is not working... how else would we be able to tell you what's wrong ? — Laurent S.
– Laurent S., Commented May 3, 2013 at 12:50
@bartdude , like i wrote in OP - array_diff($big_array, $small_array); @kingkero , the $big_array has a lot of arrays, i just showed 1 here because as an example, but it has more than 1 — Edgar
– Edgar, Commented May 3, 2013 at 12:52

liyakat · Accepted Answer · 2019-12-30 10:10:18Z

14

yes you can use below function to get you perfect answer

function arrayRecursiveDiff($aArray1, $aArray2) {
  $aReturn = array();

  foreach ($aArray1 as $mKey => $mValue) {
    if (array_key_exists($mKey, $aArray2)) {
      if (is_array($mValue)) {
        $aRecursiveDiff = arrayRecursiveDiff($mValue, $aArray2[$mKey]);
        if (count($aRecursiveDiff)) { $aReturn[$mKey] = $aRecursiveDiff; }
      } else {
        if ($mValue != $aArray2[$mKey]) {
          $aReturn[$mKey] = $mValue;
        }
      }
    } else {
      $aReturn[$mKey] = $mValue;
    }
  }
  return $aReturn;
} 

  $arr1 =    arrayRecursiveDiff($big_array,$small_array);

output

as you need

Array

(
    [0] => Array
        (
            [1] => Array
                (
                    [correct] => 
                    [answer] => false answer2
                )

            [2] => Array
                (
                    [correct] => 
                    [answer] => false answer3
                )

            [3] => Array
                (
                    [correct] => 1
                    [answer] => correct answer
                )

        )

)

check here for more info

edited Dec 30, 2019 at 10:10

answered May 3, 2013 at 13:01

liyakat

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3 Comments

Fr0zenFyr Over a year ago

array_udiff() would be a better choice.. Just sayin..

lopata Over a year ago

when making the difference of more than 5000 values,The returned array has 2% of its values that miss the 3rd and 4th associative key of the sub-array

Nick Over a year ago

If you are going to copy code from elsewhere, please attribute it. This is an exact copy of code posted as a comment on the PHP array_diff manual page.

Murali Kumar · Accepted Answer · 2014-07-06 02:29:21Z

Edited above code check whether or the the arr1 is bigger or arr2 is bigger

function arrayRecursiveDiff($aArray1, $aArray2) {

if(sizeof($aArray1) > sizeof($aArray2))
{
    $small_arr = $aArray2;
    $big_arr = $aArray1;
    $arr1_is_big = 1;
}
else
{
    $small_arr= $aArray1;
    $big_arr = $aArray2;
    $arr1_is_big = 0;
}
$aReturn = array();

foreach ($big_arr as $mKey => $mValue) {
    if (array_key_exists($mKey, $small_arr)) {
        if (is_array($mValue)) {
            $aRecursiveDiff = arrayRecursiveDiff($mValue, $small_arr[$mKey]);
            if (count($aRecursiveDiff)) { $aReturn[$mKey] = $aRecursiveDiff; }
            }
        else {
            if ($mValue != $small_arr[$mKey]) {
                $aReturn[$mKey] = $mValue;
                }
            }
    } else {
        $aReturn[$mKey] = $mValue;
    }
}
$aReturn["arr1_is_big"] = $arr1_is_big;

return ($aReturn);
}

Gummibeer · Accepted Answer · 2015-06-03 11:02:06Z

I just edited the function from Murali Kumar cause I needed one more information. It will check if the arrays are the same size and contains the same values.

function arrayRecursiveDiff($aArray1, $aArray2) {
    if(count($aArray1) > count($aArray2)) {
        $small_arr = $aArray2;
        $big_arr = $aArray1;
        $arr1_is_big = 1;
        $arr2_is_big = 0;
    } elseif(count($aArray1) < count($aArray2)) {
        $small_arr = $aArray1;
        $big_arr = $aArray2;
        $arr1_is_big = 0;
        $arr2_is_big = 1;
    } else {
        $small_arr = $aArray1;
        $big_arr = $aArray2;
        $arr1_is_big = 0;
        $arr2_is_big = 0;
    }
    $aReturn = array();

    foreach($big_arr as $mKey => $mValue) {
        if(array_key_exists($mKey, $small_arr)) {
            if(is_array($mValue)) {
                $aRecursiveDiff = arrayRecursiveDiff($mValue, $small_arr[$mKey]);
                if(count($aRecursiveDiff)) {
                    $aReturn[$mKey] = $aRecursiveDiff;
                }
            } else {
                if($mValue != $small_arr[$mKey]) {
                    $aReturn[$mKey] = $mValue;
                }
            }
        } else {
            $aReturn[$mKey] = $mValue;
        }
    }
    if($arr1_is_big)
        $aReturn["arr1_is_big"] = $arr1_is_big;

    if($arr2_is_big)
        $aReturn["arr2_is_big"] = $arr2_is_big;

    return ($aReturn);
}

mickmackusa · Accepted Answer · 2024-11-13 07:46:01Z

Your input arrays appear to have correlated data sets. To synchronous iterate each data set and filter out the differences, make array_udiff() calls inside array_map(). Demo

var_export(
    array_map(
        fn($bigSet, $smallSet) => array_udiff(
            $bigSet,
            $smallSet,
            fn($a, $b) => $a <=> $b
        ),
        $big_array,
        $small_array
    )
);

Output:

array (
  0 => 
  array (
    1 => 
    array (
      'correct' => false,
      'answer' => 'false answer2',
    ),
    2 => 
    array (
      'correct' => false,
      'answer' => 'false answer3',
    ),
    3 => 
    array (
      'correct' => true,
      'answer' => 'correct answer',
    ),
  ),
)

If you want indexed rows in the result array, just call array_values() on each filtered row.

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