Find the common values in an array of arrays

Question

I have an array of arrays.

$a = [
    [1, 2, 3],
    [2, 3, 4],
    [2, 4, 5]
];

How can I find common element which exist in all array?

In the above sample data, I'd expect to have a result array containing the value 2 because it is the only value that occurs in all rows.

Answer 1

This is a function I have made. It's just a reference for a multidimensional array.

<?php
$array1 = array('angka'=>12,'satu','2'=>'dua','tiga'=>array('dua','enam','empat'=>array('satu','lima',12)));//object
$array2 = array('dua','tiga','empat',12);//object as intersect refference

function intersect($data=NULL)
{
    if(!empty($data))
    {
        $crashed = array();
        $crashed2 = array();
        foreach($data[0] as $key=>$val)
        {
            if(!is_array($val))
            {
                $crashed[$key] = in_array($val,$data[1]);//return true if crashed (intersect)
            }
            else
            {
                $crashed2[$key] = intersect(array($val,$data[1]));
            }
            $crashed = array_merge($crashed,$crashed2);
        }
    }
    return $crashed;
}
$intersect = intersect(array($array1,$array2));
print_r($intersect);
?>

It returns a result like this:

Array ( [angka] => 1 [0] => [1] => 1 [tiga] => Array ( [0] => 1 [1] => [empat] => Array ( [0] => [1] => [2] => 1 ) ) ) 

It returns true if the value of an array matches with a reference array.

Hope the code can help you.

Answer 2

Have a look here array-intersect. You could use it like this:

$intersect = $a[0];
for ($i = 1; $i < count($a); $i++)
{
    $intersect = array_intersect($intersect, $a[$i]);
}

Answer 3

You can avoid foreach loop by

call_user_func_array('array_intersect',$a);

Answer 4

Unpack the rows into a single array_intersect() call to determine the values which occur in all rows. The result will retain the keys of the qualifying values in the first row of the array.

Code: (Demo)

$array = [
    [1, 2, 3, 4],
    [2, 3, 4, 5],
    [3, 4, 5, 6]
];

var_export(array_intersect(...$array));

Output:

array (
  2 => 3,
  3 => 4,
)

---

Spreading elements is a valid technique as long as the first level keys are numeric. If the first level keys are not numeric, just call array_values() to re-index the keys before spreading.

var_export(array_intersect(...array_values($array)));