How to remove duplicate values from a multi-dimensional array in PHP

Question

How can I remove duplicate values from a multi-dimensional array in PHP?

Example array:

Array
(
    [0] => Array
 (
     [0] => abc
     [1] => def
 )

    [1] => Array
 (
     [0] => ghi
     [1] => jkl
 )

    [2] => Array
 (
     [0] => mno
     [1] => pql
 )

    [3] => Array
 (
     [0] => abc
     [1] => def
 )

    [4] => Array
 (
     [0] => ghi
     [1] => jkl
 )

    [5] => Array
 (
     [0] => mno
     [1] => pql
 )

)

Answer 1

The user comments on the array_unique() documentation have many solutions to this. Here is one of them:

kenrbnsn at rbnsn dot com
27-Sep-2005 12:09

Yet another Array_Unique for multi-demensioned arrays. I've only tested this on two-demensioned arrays, but it could probably be generalized for more, or made to use recursion.

This function uses the serialize, array_unique, and unserialize functions to do the work.

    function multi_unique($array) {
        foreach ($array as $k=>$na)
            $new[$k] = serialize($na);
        $uniq = array_unique($new);
        foreach($uniq as $k=>$ser)
            $new1[$k] = unserialize($ser);
        return ($new1);
    }

This is from http://ca3.php.net/manual/en/function.array-unique.php#57202.

Answer 2

Another way. Will preserve keys as well.

function array_unique_multidimensional($input)
{
    $serialized = array_map('serialize', $input);
    $unique = array_unique($serialized);
    return array_intersect_key($input, $unique);
}

Answer 3

Here is another, another way. No intermediate variables are saved.

We used this to de-duplicate results from a variety of overlapping queries.

$input = array_map("unserialize", array_unique(array_map("serialize", $input)));

Answer 4

An easy to read solution, probably not the most efficient:

function arrayUnique($myArray){
    if(!is_array($myArray))
        return $myArray;

    foreach ($myArray as &$myvalue){
        $myvalue=serialize($myvalue);
    }

    $myArray=array_unique($myArray);

    foreach ($myArray as &$myvalue){
        $myvalue=unserialize($myvalue);
    }

    return $myArray;

}