How to check if an array contains empty elements?

The answer depends on how you define "empty"

$contains_empty = count($array) != count(array_filter($array));

this checks for empty elements in the boolean sense. To check for empty strings or equivalents

$contains_empty = count($array) != count(array_filter($array, "strlen"));

To check for empty strings only (note the third parameter):

$contains_empty = in_array("", $array, true);

Try using in_array:

return !in_array("", array("Paul", "", "Daniel")); //returns false