title: Laravel 4: Custom Validation Rule
body: <p>I've an <code>owners</code> table with a <code>user_id</code> field, this field can be <code>NULL</code>. because not every owner may have an user account. I need to check if the <code>user_id</code> field is <code>NUL</code>L on the <code>owners</code> table, before creating a user and updating that table. How do I do it with Laravel's Validation ?</p>