How can i get only duplicate values from an array in php?

You will need to make your function case insensitive to get the "Hello" => "hello" result you are looking for, try this method:

$arr = array(1=>'1233',2=>'12334',3 =>'Hello' ,4=>'hello', 5=>'U');

// Convert every value to uppercase, and remove duplicate values
$withoutDuplicates = array_unique(array_map("strtoupper", $arr));

// The difference in the original array, and the $withoutDuplicates array
// will be the duplicate values
$duplicates = array_diff($arr, $withoutDuplicates);
print_r($duplicates);

Output is:

Array
(
[3] => Hello
[4] => hello
)

Edit by @AlixAxel:

This answer is very misleading. It only works in this specific condition. This counter-example:

$arr = array(1=>'1233',2=>'12334',3 =>'Hello' ,4=>'HELLO', 5=>'U');

Fails miserably. Also, this is not the way to keep duplicates:

array_diff($arr, array_unique($arr));

Since one of the duplicated values will be in array_unique, and then chopped off by array_diff.

Edit by @RyanDay:

So look at @Srikanth's or @Bucabay's answer, which work for all cases (look for case insensitive in Bucabay's), not just the test data specified in the question.

10 Years Ago

Show only duplicate values from array without built in function

$arr = array(3,5,2,5,3,9);
I want to show only common elements i.e 3,5 as output.

Edited 10 Years Ago by rajendra87

Recommended Answers

How about something outside of the box:

$array = array(3, 5, 2, 5, 3, 9);
$duplicates = array_duplicates($array);

function array_duplicates(array $array)
{
    return array_diff_assoc($array, array_unique($array));
}

Jump to Post

Thanks for necroposting this dead thread back to the current list - not.

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All 7 Replies

10 Years Ago

The logic here is simple:

I am not a php developer so i am using c++ to explain this method !

int Array[6]= {3,5,2,5,3,9};

//create a for-loop for ArrayA

    for(int i=0; i<6; i++)
    {

//create a for-loop for checking element from ArrayA is equal to any other element


        for(int s=0; s<6; s++)
        {



// to check if terms are equal (note i!=s)

            if(Array[i]==Array[s] && i!=s)
            {

             //Print Array elements or store it in another array and the use any unique array function to see unique elements !
            }
        }
    }

Try to make the code for php yourself !

10 Years Ago

I saw this same question here ! if you did not post it then here is the code:

$arr = array(3,5,2,5,3,9);
foreach($arr as $key => $val){
  //remove the item from the array in order 
  //to prevent printing duplicates twice
  unset($arr[$key]); 
  //now if another copy of this key still exists in the array 
  //print it since it's a dup
  if (in_array($val,$arr)){
    echo $val . " ";
  }
}

10 Years Ago

that question was posted by me @rainbowMatrix

blocblue 238 Posting Pro in Training Featured Poster

10 Years Ago

How about something outside of the box:

$array = array(3, 5, 2, 5, 3, 9);
$duplicates = array_duplicates($array);

function array_duplicates(array $array)
{
    return array_diff_assoc($array, array_unique($array));
}

phorce 131 Posting Whiz in Training Featured Poster

10 Years Ago

Finally got there:

 0)
    {
        echo $val2 . ', ';
    }
}

?>

I doubt it will work for words, or characters, for this you will have to manipulate the array_keys.

Output:

3, 5,

Edited 10 Years Ago by phorce

renuv 0 Newbie Poster

6 Years Ago

function hasDuplicate($array) {
            $defarray = array();
        $filterarray = array();
        foreach($array as $val){
            if (isset($defarray[$val])) {
                $filterarray[] = $val;
            }
            $defarray[$val] = $val;
        }
        return $filterarray;
}

diafol

6 Years Ago

Thanks for necroposting this dead thread back to the current list - not.

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