belongsToMany

belongsToMany is a relationship type used to model a many-to-many association between two models in an ORM. In this pattern, an intermediate table called a pivot table stores the associations, with each row linking one record from each side and potentially carrying additional attributes about that link.

In Laravel's Eloquent ORM, the relation is defined on each model with the belongsToMany method. The call can include the related model class, the pivot table name, and the foreign key names for both models. If these are omitted, conventions apply: the pivot table name is the two model names in alphabetical snake_case plural form, and the foreign keys are the respective model names suffixed with _id (for example, post_id and tag_id). You can customize with belongsToMany(Tag::class, 'post_tag', 'post_id', 'tag_id').

Querying the relation returns a collection of related models. When looping, pivot data is accessible on each related model via a pivot property, and additional pivot columns can be retrieved or selected with withPivot('field'). Enabling withTimestamps() on the relation stores created_at and updated_at on the pivot table.

Common operations to manage the relation include attach, detach, and sync. attach and detach add or remove specific links; sync updates the entire set to match a given list of IDs, removing any not present. You can also update an existing pivot row with updateExistingPivot.

Example: a posts_tags pivot table connects posts and tags with post_id and tag_id. In Post, public function tags() { return $this->belongsToMany(Tag::class)->withTimestamps(); } In Tag, public function posts() { return $this->belongsToMany(Post::class)->withTimestamps(); }