Illuminate\Database\Query\Builder::mergeBindings PHP Method

    public function mergeBindings(Builder $query)
    {
        $this->bindings = array_merge_recursive($this->bindings, $query->bindings);
        return $this;
    }

 /**
  * Add a relationship count condition to the query.
  *
  * @param  string  $relation
  * @param  string  $operator
  * @param  int     $count
  * @return \Illuminate\Database\Eloquent\Builder
  */
 public function has($relation, $operator = '>=', $count = 1)
 {
     $instance = $this->model->{$relation}();
     $query = $instance->getRelationCountQuery($instance->getRelated()->newQuery());
     $this->query->mergeBindings($query->getQuery());
     return $this->where(new Expression('(' . $query->toSql() . ')'), $operator, $count);
 }