Get Removed/Duplicates Key values from Array PHP

Question

First of all this is not a duplicate as i haven't found any info about this. We can successfully remove duplicate values using the following from an array for example:

 $messages=   Array ( 
        [0] => Array ( [user] => 2224 [sending_time] => 1536513903 [read_time] => 1536513941 [content] => sad [recipient_status] => read ) 
        [1] => Array ( [user] => 3310 [sending_time] => 1536513903 [read_time] => 1536513941 [content] => sad [recipient_status] => read ) 
        [2] => Array ( [user] => user1 [sending_time] => 1536513874 [read_time] => 1536567672 [content] => def [recipient_status] => read ) 
        [3] => Array ( [user] => user1 [sending_time] => 1536513532 [read_time] => 1536513745 [content] => abc [recipient_status] => read ) 
    )

Using the following i can remove the duplicates(by key):

        $MSGS_array  = array();
        foreach ($messages as $message) {
            $MSGS_array[$message['user']] = $message;
        }

But the question is how can i get the removed user key value?

OR

How can i get all the duplicates having key user and their value(s) in an array from the array above?

Expected Output:

The output should only contain the removed/duplicates Like:(i just need the duplicates with they key user)

 $output=   Array (
        [0] => Array ( [user] => user1 ) 
        [1] => Array ( [user] => user1 ) 
 );

OR

 $output=   Array (
        [0] => Array ( [user] => user1 [sending_time] => 1536513874 [read_time] => 1536567672 [content] => def [recipient_status] => read ) 
        [1] => Array ( [user] => user1 [sending_time] => 1536513532 [read_time] => 1536513745 [content] => abc [recipient_status] => read ) 
 );

None of the entries in your example are exact duplicates of one of the others... what makes an entry a duplicate? — Nick
– Nick, Commented Nov 25, 2018 at 6:00
please check [3] and [4] array having value 'user1' similar. — MR_AMDEV
– MR_AMDEV, Commented Nov 25, 2018 at 6:01

Nick · Accepted Answer · 2018-11-25 07:32:33Z

2

Here is one way to find the duplicate messages. First we find the non-unique users by checking the count of the values of user. Then we filter the messages in $messages by seeing if the user is in the non-unique users array:

$non_unique_users = array_filter(array_count_values(array_column($messages, 'user')), function ($v) { return $v != 1; });
$duplicate_messages = array_filter($messages, function ($v) use($non_unique_users) { return array_key_exists($v['user'], $non_unique_users); });
print_r($duplicate_messages);

Output:

Array ( 
    [2] => Array ( [user] => user1 [sending_time] => 1536513874 [read_time] => 1536567672 [content] => def [recipient_status] => read ) 
    [3] => Array ( [user] => user1 [sending_time] => 1536513532 [read_time] => 1536513745 [content] => abc [recipient_status] => read ) 
)

Demo on 3v4l.org

Update

To just return an array of the user keys, you can apply array_map to the $duplicate_messages array:

$duplicate_users = array_map(function ($v) { return array('user' => $v['user']); }, $duplicate_messages);

or you can derive it directly from the $messages and $non_unique_users arrays:

$duplicate_users = array_map(function ($v) use($non_unique_users) { if (array_key_exists($v['user'], $non_unique_users)) return array('user' => $v['user']); }, $duplicate_messages);

In both cases the output is

Array ( 
    [2] => Array ( [user] => user1 ) 
    [3] => Array ( [user] => user1 ) 
)

Demo on 3v4l.org

edited Nov 25, 2018 at 7:32

answered Nov 25, 2018 at 6:27

Nick

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2 Comments

MR_AMDEV Over a year ago

Thanks this is working but how can i get the **user key and value only **without the rest sending_time,read_time etc.

Nick Over a year ago

@MR_AMDEV see my edit. That should give you what you want.

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