Syntax of array_intersect
array array_intersect(array array1, array array2[, … array arrayN])
Returns an array consisting of every element in array1 that also exists in every other array
Example of array_intersect in PHP
<?php
$input = array("a" => 1, "b" => 1, "c" => 2);
$flipped = array_flip($input);
print_r($flipped);
?>
Array ( [1] => b [2] => c )