public static function add( $key, $item, &$arr ) 
	{	
		if( !is_array( $arr ) ) 
		{
			throw new \InvalidArgumentException('CCArr::add - second argument has to be an array.');
		}

		if ( !is_array( static::get( $key, $arr ) ) )
		{
			return static::set( $key, array( $item ), $arr );
		}

		return static::set( $key, static::push( $item, static::get( $key, $arr ) ), $arr );
	}