在多维数组中搜索重复项，并返回重复值和数组键

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");

// 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);

First combine all the names into one array, with names as keys and arrays of generation indexes as values:

foreach ($ancestors as $generation_key => $generation) {
    foreach ($generation as $name) {
        $combined[$name][] = $generation_key;
    }
}

Then limit the combined results to values having more than one instance of the name:

$duplicates = array_filter($combined, function($x) { return count($x) > 1; });

Then convert the arrays to single values using min:

foreach ($duplicates as &$value) {
    $value = min($value);
}
unset($value);

We have to compare each row with following rows, so row 1 with 2 and 3, row 2 with 3, row 3 with nothing (it is already compared). To do this, we use a base-1 for to loop through all $ancestors elements except last, then we compare each name with greater ancestors:

$result = array();
/* Loop count($ancestors) -1: */
for( $i = 1; $i<count( $ancestors ); $i++ )
{
    /* Loop for each name: */
    foreach( current( $ancestors ) as $val )
    {
        /* If name is already in result, skip: */
        if( isset( $result[$val] ) ) continue;
        /* Loop for each following ancestors: */
        foreach( array_slice( $ancestors, $i, Null, True ) as $key => $row )
        {
            if( in_array( $val, $row ) ) $result[ $val ] = key( $ancestors );
        }
    }
    next( $ancestors );
}

For this $ancestors:

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

the result is:

Array
(
    [Andrew] => 1
    [Adele] => 1
    [Bill] => 2
    [Cathy] => 3
)