Laravel - Relationships - One To One

A one-to-one relationship is a very basic type of database relationship. For example, a User model might be associated with one Phone model. To define this relationship, we will place a phone method on the User model. The phone method should call the hasOne method and return its result. The hasOne method is available to your model via the model's Illuminate\Database\Eloquent\Model base class:


The first argument passed to the hasOne method is the name of the related model class. Once the relationship is defined, we may retrieve the related record using Eloquent's dynamic properties. Dynamic properties allow you to access relationship methods as if they were properties defined on the model:

    $phone = User::find(1)->phone;

Eloquent determines the foreign key of the relationship based on the parent model name. In this case, the Phone model is automatically assumed to have a user_id foreign key. If you wish to override this convention, you may pass a second argument to the hasOne method:

    return $this->hasOne(Phone::class, 'foreign_key');

Additionally, Eloquent assumes that the foreign key should have a value matching the primary key column of the parent. In other words, Eloquent will look for the value of the user's id column in the user_id column of the Phone record. If you would like the relationship to use a primary key value other than id or your model's $primaryKey property, you may pass a third argument to the hasOne method:

    return $this->hasOne(Phone::class, 'foreign_key', 'local_key');