在多维数组中搜索重复项，并返回重复值和数组键

Question

I have the following multidimensional array:

$ancestors = array(
[1] =>array("Andrew","Adele"), 
[2] =>array("Bertha","Bill","Billy","Blake"), 
[3] =>array("Cathy","Case","Cory","Creek","Andrew","Ceaser","Cece","Childer"));

I am trying to search the rows and return duplicate values along with the array key of the lowest number the duplicate appears and return values to an associative array:

$common = array("Andrew"=>"1");

Answer 1

// merge all array in one
$new = array();
foreach($ancestors as $i)
   $new = array_merge($new, $i);

// make array value => count and sort in in descendant order
$ar = array_count_values($new);
arsort($ar);

// save result array while count > 1
$result = array();
foreach($ar as $k => $v) {
  if ($v < 2) break;
  $result[$k] = array_search($k, $new) + 1;
}

print_r($result);