Check and return duplicates array php

Question

Hello, I would like to check if my array has any duplicates and return the duplicated values in an array. I want this to be as efficient as possible.

Example :$array = array(1,2,2,4,5)
function returndup($array) should return 2 ;

if array is array(1,2,1,2,5);
it should return an array with 1,2

Also the initial array is always 5 positions long

Answer 1

function returndup($array) 
{
    $results = array();
    $duplicates = array();
    foreach ($array as $item) {
        if (in_array($item, $results)) {
            $duplicates[] = $item;
        }

        $results[] = $item;
    }

    return $duplicates;
}

Answer 2

You can get the difference of the original array and a copy without duplicates using array_unique and array_diff_assoc:

array_diff_assoc($arr, array_unique($arr))

Answer 3

function array_dup($ar){return array_unique(array_diff_assoc($ar,array_unique($ar)));}

Should do the trick.

Answer 4

in addition to gumbo's answer:

function returndup($arr)
{
  return array_diff_key($arr, array_unique($arr));
}

Answer 5

You can do like this:

function showDups($array)
{
  $array_temp = array();

   foreach($array as $val)
   {
     if (!in_array($val, $array_temp))
     {
       $array_temp[] = $val;
     }
     else
     {
       echo 'duplicate = ' . $val . '<br />';
     }
   }
}


$array = array(1,2,2,4,5);
showDups($array);

Output:

duplicate = 2

Answer 6

this will be ~100 times faster than array_diff

$dups = array();
foreach(array_count_values($arr) as $val => $c)
    if($c > 1) $dups[] = $val;