array intersect

1array_intersect(array $array, array ...$arrays): array
2
3/* Returns an array containing all of the values in array whose 
4   values exist in all of the parameters. */

1$array1 = [1, 2];
2$array2 = [2, 3, 4];
3$commonValue = array_intersect($array1, $array2);
4//$commonValue = 2
5// If you have X number of arrays you can do:
6$array1 = [1, 2];
7$array2 = [2, 3, 4];
8$arrayOfArrays = [$array1, $array2];
9$commonValue = array_intersect(...$arrayOfArrays);