How to remove duplicate data in an array?

Question

I have the following array:

I want to remove duplicate entry of [Import][product_id]. So my expected result is :

Array
(
    [0] => Array
        (
            [Import] => Array
                (
                    [product_id] => 1
                    [id] => 1
                    [category_id] => 1
                    [amount] => 50
                    [cost] => 8320
                    [paid] => 0
                    [comment] => transportation and others cost: 100  
                    [created] => 2015-06-22 12:09:20
                )

            [0] => Array
                (
                    [total_sell] => 6
                )

        )

    [1] => Array
        (
            [Import] => Array
                (
                    [product_id] => 2
                    [id] => 2
                    [category_id] => 2
                    [amount] => 15
                    [cost] => 3000
                    [paid] => 0
                    [comment] => 
                    [created] => 2015-06-22 12:10:36
                )

            [0] => Array
                (
                    [total_sell] => 1
                )

        )

)

Would you write a function to filter this type of array and produce expected result. I have been googling for 2 days but no luck.

When encountering semi-duplicates, which version of product_id do you want to keep in the final result? It looks like "first encountered". Is that right? — Drakes
– Drakes, Commented Jun 23, 2015 at 23:47

dave · Accepted Answer · 2015-06-23 23:55:57Z

3

This is a handy one liner that should do the trick:

$unique= array_map("unserialize", array_unique(array_map("serialize", $original)));

If the underlying arrays are not identical, that won't work, in which case I think you could do:

$unique = array_intersect_key($original ,
              array_unique(
                  array_map(function($item) {
                      return $item['Import']['product_id'];
                  }, $original)
              )
           );

Tested: http://sandbox.onlinephpfunctions.com/code/8aee5cbd614e0ddd1a03dfaa7e98c72fbbe7d68d

edited Jun 23, 2015 at 23:55

answered Jun 23, 2015 at 23:36

dave

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4 Comments

Drakes Over a year ago

Will this work if only the product_id's are the same, but other values are not the same? (I didn't downvote btw)

Abdus Sattar Bhuiyan Over a year ago

$unique= array_map("unserialize", array_unique(array_map("serialize", $old_array))); This does not work for me

Drakes Over a year ago

We should ask the OP how he decides which version of product_id he wants to keep in the final result. It looks like "first encountered"

Abdus Sattar Bhuiyan Over a year ago

Yes. "first encountered" will be kept in final result

Drakes · Accepted Answer · 2015-06-24 04:09:12Z

Here is a quick stable sort and reduce which runs in linearithmic time. First-encountered product Id's are kept, and entries with duplicate product Id's are ignored.

// Stable sort
sort($in);

// Reduce
$out = array_reduce($in, function(&$acc, &$item){ 
    if($item['Import']['product_id'] !== @$acc[sizeof($acc)-1]['Import']['product_id']) {
       $acc[] = $item;    
    }
    return $acc;
}, []);

Demo: http://ideone.com/BP0eUJ

Update: Here is an even better linear-time algorithm that does the same as above using a fast "hash table" lookup. Again, the first-encountered product Id is kept and subsequent ones of the same Id are ignored.

$out = []; 
$hashTable = [];
foreach($in as $item) {
  $pid = $item['Import']['product_id'];
  if(!isset($hashTable[$pid])) {
    $out[] = $item; 
    $hashTable[$pid] = true;
  }
}

Demo: http://ideone.com/5RF0og

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