在PHP中测试没有数组交集

Question

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?

Answer 1

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");