How do you find most common array in multidimensional array using PHP

Question

I need to find the most common (most occurring) array in a multidimensional array. Not the most common values like this post - Find Common most values in multidimensional array in PHP - but rather the most common combination.

For example, if I have the following:

$a1=array(
    array('704322062'),
    array('678073776', '704322062'),
    array('678073776', '704322062'),
    array('704322064'),
    array('704322062'),
    array('678073776'),
    array('678073776', '704322062')
);

I want to be able to detect that the array that occurs most often is array('678073776', '704322062') not that the string '704322062' is most common.

I've tried using array_intersect but couldn't get it working for this scenario.

Thanks!

C3roe · Accepted Answer · 2021-04-16 11:47:58Z

2

array_count_values only works with scalar values, not when the items are arrays themselves. But we can still use that function, if we transform your arrays into strings first - by encoding them as JSON.

// fill temp array with items encoded as JSON
$temp = [];
foreach($a1 as $item) {
  $temp[] = json_encode($item);
}

// count how many times each of those values occurs
$value_counts = array_count_values($temp);
// sort by number of occurrence, while preserving the keys
ksort($value_counts);

// pick the first key from the temp array
$first = array_key_first($value_counts);

This will get you ["678073776","704322062"] in $first now - you can json_decode it again, if you want your “original” array.

Note that this does not take into account, that two arrays could occur the same amount of times - then it will just pick the “random” first one of those. If you need to handle that case as well somehow, then you can determine the maximum value in $temp first, and then filter it by that value, so that only those keys of the corresponding arrays will be left.

answered Apr 16, 2021 at 11:47

C3roe

97.6k15 gold badges100 silver badges172 bronze badges

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

3 Comments

KIKO Software Over a year ago

You don't address the issue that array('678073776', '704322062') could be equal to array('704322062', '678073776'). The question doesn't say anything about this.

C3roe Over a year ago

@KIKOSoftware good point – should that also be a requirement, then $item could be sorted first, before it gets encoded as JSON and added to the temp array.

kh_9 Over a year ago

Thanks so much - this has worked perfectly @CBroe And I just dropped in a sort on $item to @KIKOSoftware's point. Thank you both!

Collectives™ on Stack Overflow

How do you find most common array in multidimensional array using PHP

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related