Get the keys for duplicate values in an array

Question

I have the following array:

$myarray = Array(\"2011-06-21\", \"2011-06-22\", \"2011-06-22\", \"2011-06-23\", \"2011-06-23\", \"2011-06-24\", \"2011-06-24\",         


        

Answer 1

here is a code dude

   $your_array = array(0 => '2011-06-21', 1 => '2011-06-22', 2 => '2011-06-22', 3 => '2011-06-23', 4 =>
'2011-06-23', 5 => '2011-06-24', 6 => '2011-06-24', 7 => '2011-06-25', 8 => '2011-06-25', 9 
=> '2011-06-26', 10 => '2011-06-26', 11 => '2011-06-27', 12 => '2011-06-27', 13 => '2011-06-  
28', 14 => '2011-06-29', 15 => '2011-06-29', 16 => '2011-06-30', 17 => '2011-06-30', 18 => 
'2011-07-01', 19 => '2011-07-01', 20 => '2011-07-02', 21 => '2011-07-02', 22 => '2011-07-03', 
23 => '2011-07-03', 24 => '2011-07-04', 25 => '2011-07-04', 26 => '2011-07-05', 27 => '2011-
07-05', 28 => '2011-07-06', 29 => '2011-07-06', 30 => '2011-07-07', 31 => '2011-07-07');

$keys_of_duplicated = array();
$array_keys = array();

foreach($your_array as $key => $value) {
    //- get the keys of the actual value
    $array_keys = array_keys($your_array, $value);

    //- if there is more then one key collected we register it
    if(count($array_keys) > 1) {
        //- foreach key that have the same value we check if i'ts already registered
        foreach($array_keys as $key_registered) {
            //- if not registered we register it
            if(!in_array($key_registered,  $keys_of_duplicated)) {
                 $keys_of_duplicated[] = $key_registered;
            }
        }
    }
}

var_dump($keys_of_duplicated);

$keys_of_duplicated is now the array that contains the keys of duplicated arrays ;) bye

Answer 2

function getDuplicateValueKeys($my_arr, $clean = false) 
{
    if ($clean) {
        return array_unique($my_arr);
    }
    $dups = array();
    $new_arr = array();
    $dup_vals = array();

    foreach ($my_arr as $key => $value) {
        if (!isset($new_arr[$value])) {
            $new_arr[$value] = $key;
        } else {
            array_push($dup_vals,$value);
        }
    }

    foreach ($my_arr as $key => $value) {
        if (in_array($value, $dup_vals)) {
            if (!isset($dups[$value])) {
                $dups[$value]=array($key);
            }else{
                array_push($dups[$value],$key);
            }
        }
    }

    return $dups;
}

Answer 3

Another example:

$array = array(
  'a',
  'a',
  'b',
  'b',
  'b'
);
echo '<br/>Array: ';
print_r($array);
// Unique values
$unique = array_unique($array);
echo '<br/>Unique Values: ';
print_r($unique);
// Duplicates
$duplicates = array_diff_assoc($array, $unique);
echo '<br/>Duplicates: ';
print_r($duplicates);
// Get duplicate keys
$duplicate_values = array_values(array_intersect($array, $duplicates));
echo '<br/>duplicate values: ';
print_r($duplicate_values);

Output:

Array :Array ( [0] => a [1] => a [2] => b [3] => b [4] => b ) 
Unique Values :Array ( [0] => a [2] => b ) 
Duplicates :Array ( [1] => a [3] => b [4] => b ) 
Duplicate Values :Array ( [0] => a [1] => a [2] => b [3] => b [4] => b )