Check if variable empty

Question

Code:

if ($user_id == NULL || $user_name == NULL || $user_logged == NULL) {
    $user_id = '-1';
    $user_name = NULL;
    $user_logged = NULL;
}
if ($user_admin == NULL) {
    $user_admin = NULL;
}

1. Is there any shortest way to do it?
2. And if I am right, it should be tested with is_null?
3. Is It possible $user_id, $user_name and $user_logged to write in one line (maybe array?) without repeating NULL?

Answer 1

To check if the variable if really null you can use the identity operator:

$user_id === NULL  // FALSE == NULL is true, FALSE === NULL is false
is_null($user_id)

 To check if the variable is not set use this:

!isset($user_id)

If the variable is not empty, an empty string, zero:

empty($user_id)

If you want to test whether a variable is not an empty string,! will also be sufficient:

!$user_id

I hope this helps you.