Check and return duplicates array php

Question

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:

Answer 1

this will be ~100 times faster than array_diff

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

Answer 2

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 3

If you need a solution that will work with an array of arrays (or any array values other than integers or strings) try this:

function return_dup( $arr ) {
    $dups = array();
    $temp = $arr;
    foreach ( $arr as $key => $item ) {
        unset( $temp[$key] );
        if ( in_array( $item, $temp ) ) {
            $dups[] = $item;
        }
    }
    return $dups;
}


$arr = array(
    array(
        0 => 'A',
        1 => 'B',
    ),
    array(
        0 => 'A',
        1 => 'B',
    ),
    array(
        0 => 'C',
        1 => 'D',
    ),
    array(
        0 => 'C',
        1 => 'D',
    ),
    array(
        0 => 'E',
        1 => 'F',
    ),
    array(
        0 => 'F',
        1 => 'E',
    ),
    array(
        0 => 'Y',
        1 => 'Z',
    ),
);

var_export( return_dup( $arr ) );
/*
array (
    0 => array (
        0 => 'A',
        1 => 'B',
    ),
    1 => array (
        0 => 'C',
        1 => 'D',
    ),
)
*/

Answer 4

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

Should do the trick.

Answer 5

I have found another way to return duplicates in an array

function printRepeating($arr, $size) 
{ 
    $i; 
    $j; 
    for($i = 0; $i < $size; $i++) 
        for($j = $i + 1; $j < $size; $j++) 
            if($arr[$i] == $arr[$j]) 
                echo $arr[$i], " "; 
}  



printRepeating($array, sizeof($array,0);

Answer 6

$duplicate_array = array();

  for($i=0;$i<count($array);$i++){

    for($j=0;$j<count($array);$j++){

      if($i != $j && $array[$i] == $array[$j]){

        if(!in_array($array[$j], $duplicate_array)){

          $duplicate_array[] = $array[$j];

        }

      }

    }    

  }