如何检查array_intersect的结果是否为空？

Question

I am trying to check the result of an array_intersect as a regular array but it always returns true even if the array is empty.

      $lecturedayssplit1 = preg_split("/(?=[A-Z])/", "TF");
      $lecturedayssplit2 = preg_split("/(?=[A-Z])/", "MTh");
      $lectolec=array_intersect($lecturedayssplit1,$lecturedayssplit2);
        if (count($lectolec) > 0) {
            echo "Yeah!!!";
            print_r($lectolec);
        } else {
            echo "Nooo!";
            print_r($lectolec);
        }

$lectolec in the problem shouldn't return a count greater than 0 because there is no intersection between the two arrays. I also tried if (empty($lectolec)) but it also didn't work. Hopefully someone can help out. Thanks in advance!

Answer 1

Because you are using a "zero-width positive lookahead" (?=[A-Z]) regex, it is matching an empty sequence in the beginning of each test. Therefore, array_intersect matches that empty sequence in both.

You can use the flag PREG_SPLIT_NO_EMPTY to ignore those empty results.

$lecturedayssplit1 = preg_split("/(?=[A-Z])/", "TF", -1, PREG_SPLIT_NO_EMPTY);
$lecturedayssplit2 = preg_split("/(?=[A-Z])/", "MTh", -1, PREG_SPLIT_NO_EMPTY);