array_intersect Computes the intersection of arrays arrayarray_intersect arrayarray1 arrayarray2 array ... array_intersect returns an array containing all the values of array1 that are present in all the arguments. Note that keys are preserved. "green", "red", "blue"); $array2 = array ("b" => "green", "yellow", "red"); $result = array_intersect ($array1, $array2); ]]> This makes $result have green [0] => red ) ]]> Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is the same. This was broken in PHP 4.0.4! See also array_intersect_assoc, array_diff, and array_diff_assoc.