Database relationships for a flagging system in Laravel 5.2

Problem

I'm building an application where are many things a user can flag. Lets take these example things a user can flag:

• Another user
• An image
• A comment
• A tag

So I want one flagging table to deal with flagging all these things, but with my vision and to stick to Laravel's conventions so I can make use of relationship methods, I'd have to do something like this for the flags table...

---

My "solution"

+----+---------+----------+--------+------------+-----------------------------+
| id | user_id | image_id | tag_id | comment_id | message                     |
+----+---------+----------+--------+------------+-----------------------------+
| 1  | 3       | null     | null   | null       | I'm building an application |
+----+---------+----------+--------+------------+-----------------------------+
| 2  | null    | 45       | null   | null       | This image is NSFW!         |
+----+---------+----------+--------+------------+-----------------------------+
| 3  | null    | null     | 234    | null       | Tag includes bad content... |
+----+---------+----------+--------+------------+-----------------------------+
| 4  | null    | null     | null   | 125        | Spamming!!!                 |
+----+---------+----------+--------+------------+-----------------------------+

Now this way, this flagging system is not scalable at all! If I want to be able to flag things in the future, I'd have to add a column and map it etc.

I don't like this messy solution and I can't think of another Laravel-y way to do this!

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I need help to figure out a scalable way to handle flags with one table for multiple things in a Laravel 5.2 way, with Eloquent examples if possible. Help would be highly appreciated.

via Chebli Mohamed