BelongsTo

BelongsTo is a relationship type used in Laravel's Eloquent ORM to define the inverse of a one-to-many or one-to-one association. It indicates that the current model belongs to another model, which holds the foreign key. In database terms, the child table contains a foreign key referencing the parent table (for example, a comments table with post_id referencing posts.id).

In Eloquent, you declare it in the child model with a method named after the relationship, returning a belongsTo call. Example:

class Comment extends Model {

public function post() {

return $this->belongsTo(Post::class);

}

}

Usage typically involves accessing the related model via the relation property, such as $comment->post, which returns the associated Post model. You can set or change the relation with $comment->post()->associate($post) and then save the child model. Eager loading improves performance when retrieving multiple children with their parents using with('post').

Customization and keys:

The foreign key and the related key can be overridden. For example:

return $this->belongsTo(Post::class, 'custom_post_id', 'custom_id');

By default, the foreign key is the snake_case name of the relationship method with _id appended (e.g., post_id), and the related key defaults to the parent model’s primary key, typically id.

Relation direction and alternatives:

BelongsTo is defined on the child side of the relationship. The opposite side is usually defined with hasMany or hasOne on the parent model. Understanding belongsTo helps structure data navigability and database integrity in ORM-based applications.