Finding common value among sub-arrays in a multidimensional array

Question

I have the following array:

Array
(
    [0] => Array
        (
            [0] => 87
            [1] => 58
            [2] => 85
            [3]          


        

Answer 1

If there is a mistake in your example and there should be 58 in the [0] element of 'root' array you should just run

$res = $arr[0]; foreach($arr as $elem) $res = array_intersect($res, $elem);

More general solution (nested arrays):

<?php
//$arr -> your multidimensional array
function array_intersect_recursive($arr) {
  $first = true;
  foreach($arr as $elem) {
    if(is_array($elem)) $elem = array_intersect_recursive($arr);
    if($first) { $first = false; $res = $elem; } 
    else $res =  array_intersect($res, $elem);
  } 

}

I haven't tested it, but I hope you get the idea.

Answer 2

This works for me:

function multi_intersect($arr) {
   $return = array();
   foreach ($arr as $a) {
       foreach ($arr as $b) {
           if ($a === $b) continue;
           $return = array_merge($return, array_intersect($a, $b));
       }
   }
   return array_unique($return);
}

Should get you:

Array
(
    [0] => 58
)

The above will work if you have a common number in at least two of the sub-arrays.

After your edit:

You can simply use call_user_func_array on array_intersect, if you want to find numbers that are contained in all sub-arrays:

$intersect = call_user_func_array('array_intersect', $arr);