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; }
is_null
$user_id
$user_name
$user_logged
NULL
如果要测试变量是否 确实 是NULL,请使用标识运算符:
$user_id === NULL // FALSE == NULL is true, FALSE === NULL is false is_null($user_id)
如果要检查是否未设置变量:
!isset($user_id)
或者,如果变量不为空,则为空字符串,零,..:
empty($user_id)
如果要测试变量是否不是空字符串,!也将足够:
!
!$user_id