Problem with update_post_meta function

Hi, I’m developing a theme and I needed to create a meta field to count the hits for each post.

Follows the code:

function getPostViews($postID){
    $count_key = '_post_views_count';
    $count = get_post_meta($postID, $count_key, true);
    if($count==''){
        delete_post_meta($postID, $count_key);
        add_post_meta($postID, $count_key, '0');
        return "0 View";
    }
    return $count.' Views';
}
function setPostViews($postID) {
    $count_key = 'post_views_count';
    $count = get_post_meta($postID, $count_key, true);
    if($count==''){
        $count = 0;
        delete_post_meta($postID, $count_key);
        add_post_meta($postID, $count_key, '0');
    }else{
        $count++;
        update_post_meta($postID, $count_key, $count);
    }
}

Well, to test it I created 3 posts and when I hit the post #1, the counter of the post #1 and post #2 are increased simultaneously. The same issue occurs when I hit any post: the next post counter is increased too. Only the last post (most recent) works fine.

The functions are called in the single.php file using the get_the_ID() function as the parameter.