php - check if variable empty

Question

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 right, it should be tested with is_null?
3. It's possible $user_id, $user_name and $user_logged write in one line (maybe array?) without repeating NULL ?

question from:https://stackoverflow.com/questions/8777591/check-if-variable-empty

Answer 1

If you want to test whether a variable is really NULL, use the identity operator:

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

If you want to check whether a variable is not set:

!isset($user_id)

Or 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