Question

Is there a way to look inside an array and pull out the keys that have keys with matching values? Questions like this have been asked, but I’m not finding anything conclusive.

So if my array looks like this

Array
(
    [0] => Array
        (
            [title] => Title 1
            [type] => 
            [message] => 
        )

    [1] => Array
        (
            [title] => Title 2
            [type] => 
            [message] => 
        )

    [2] => Array
        (
            [title] => Title 3
            [type] => 
            [message] => 
        )

    [3] => Array
        (
            [title] => Title 2
            [type] => Limited
            [message] => 39
        )

    [4] => Array
        (
            [title] => Title 4
            [type] => Offline
            [message] => 41
        )

    [5] => Array
        (
            [title] => Title 5
            [type] => 
            [message] => 
)

And I want to get this

Array
(
    [1] => Array
        (
            [title] => Title 2
            [type] => 
            [message] => 
        )


    [3] => Array
        (
            [title] => Title 2
            [type] => Limited
            [message] => 39
        )
)

Answer 1

$titlesCount = array_count_values(array_map(function($item){ return $item['title']; }, $input));
$output = array_filter($input, function($item) use(&$titlesCount){ return $titlesCount[$item['title']] > 1; });

where $input is the original array and $output is the result.

It counts each distinct value of title and returns only those that occur more than once.