I have the following code:
$result = array_intersect($contacts1, $contacts2);
This generates:
Array
(
[21] =>
[22] =>
[23] =>
[24] =>
[25] =>
[26] =>
[28] =>
I have the following if statement:
if (empty($result)) { // i.e. NO INTERECTION
I just realized that this will not work as a test for no intersection because many elements are produced, all with the value null. Given this what is the best way to test for intersection of 2 arrays?
If NULLs are in the array, then array_intersect will return them as being in both arrays.
$contacts1 = array("bob", "jane", NULL, NULL);
$contacts2 = array("jim", "john", NULL, NULL);
$result = array_intersect($contacts1, $contacts2);
print_r( $result );
Array ( [2] => [3] => )
You can filter each array before the intersection using array_filter. It takes a callback function, but by default all entries equal to FALSE will be removed, including NULLs.
$result2 = array_intersect(array_filter($contacts1), array_filter($contacts2));
print_r( $result2 );
Array ( )
Use the callback if you want to specifically filter only NULLs, or what your requirements are.
function mytest($val) {
return $val !== NULL;
}
$result3 = array_intersect(array_filter($contacts1, "mytest"), array_filter($contacts2, "mytest"));
print_r( $result3 );
Array ( )
You can check if all the values are null (if you know that no null's can exist in your arrays). You can use array_filter function.
For example:
$result = array_filter(array_intersect($contacts1, $contacts2));
That way, all nulls will be removed, and the result (if no intersecion exists) will be an empty array.
UPDATE: As said in the comment, this will remove also non-null values. A revised version is to use the callback function:
function filterOnlyNulls($elem) {
return $elem !== null;
}
$result = array_filter(array_intersect($contacts1, $contacts2), "filterOnlyNulls");
