Check if array value is empty in an existing array

Here is my array ouput

 Array
(
    [1] => 1
    [2] => 2
    [3] => 
)

How do I know the [3] => is empty?

Solution:

$array = array('one', 'two', '');

if(count(array_filter($array)) == count($array)) {
    echo 'OK';
} else {
    echo 'ERROR';
}