Illuminate\Database\Eloquent\Model::getKeyName PHP Method

    public function getKeyName()
    {
        return $this->primaryKey;
    }

 /**
  * Get JWT identifier.
  * Defaults to the model id.
  *
  * @return string|int
  */
 public function getJWTIdentifier()
 {
     if (!method_exists($this->model, 'getJWTIdentifier')) {
         return $this->model->{$this->model->getKeyName()};
     }
     return $this->model->getJWTIdentifier();
 }