Many-to-many relationship with many tables?

Question

Laravel

Hello.
The site has news, videos, galleries, people. All entities have tags. Now there are 4, but there may be more.
I'd like to create one table where I link them to a tag. The tag table is common to all.
Like this:
| id | material_id | tag_id | material_type |
|.1.|.........1.........|.....1....|........news..... ..|
|.2.|.........1.........|.....1....|........video..... ..|
|.3.|.........1.........|.....1....|.......gallery...... |
I tried to do this, but I ran into a key constraint - I don't know how to set a foreign key for an intermediate table.
How to register a foreign key on n tables?

Answer 1

https://laravel.ru/docs/v5/eloquent-relationships#mmp