How to use self referential N-M relationship to make 2 users friends using RedBean PHP ORM?

I am working with PHP and RedBean PHP ORM. I have a table user like so:

id | username
---|---------
 1 | Alice
 2 | Bob

I want Alice and Bob to become friends. So I want to create M-M junction table friend that will look something like this:

id | friend_1_id | friend_2_id
---|-------------|------------
 1 |           1 |           2

friend_1_id and friend_2_id should be a foreign key reference to user.

In RedBean PHP ORM documentation at the bottom of Many-to-Many page there is a section titled "Self referential N-M". Here is the content of that section:

You can have a shared list containing beans of the same type as the owner of the list:

$friends = $friend->sharedFriend;

In this case RedBeanPHP will operate in a special self-referential many-to-many relationship mode. It will not only retrieve all friends of $friend, but also all other friends that are associated with $friend.

I don't find this section to be informative enough. I suspect that this is exactly what I need, however, I cannot figure out how to make it work. Here is what I tried:

$u1 = R::findOne("user", "id = 1");
$u2 = R::findOne("user", "id = 2");
$u1->sharedFriend = $u2;
R::store($u1);

Instead of creating friend table and linking 2 users it added sharedFriend_id column to user table and now it looks like this:

id | username | sharedFriend_id
---|----------|----------------
 1 | Alice    | 2
 2 | Bob      | NULL

Questions:

• How can I implement self-referential N-M with RedBean PHP?
• If "self-referential N-M" is not the correct approach for the problem I want to solve then what would be the most "RedBean PHP"-ish way of making two users friends?

posted over 1 year ago

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