src/Primitive/Container/Container.php
public function merge($items)
    {
        if ( ! $this->isArrayable($items))
        {
            throw new BadMethodCallException('Argument 1 must be array, Container or implement Arrayable interface');
        }

        return new static(array_merge($this->items, $this->retrieveValue($items)));
    }
public function merge($items)
    {
        if ( ! $this->isArrayable($items))
        {
            throw new BadMethodCallException('Argument 1 must be array, Container or implement Arrayable interface');
        }

        return new static(array_merge($this->items, $this->retrieveValue($items)));
    }
Merge Arrayable with Container.

@param  mixed $items
@throws BadMethodCallException
@return $this