public function map(callable $callable)
    {
        $keys = array_keys($this->items);
        $results = array_map($callable, $this->items, $keys);

        return new self($results);
    }
public function map(callable $callable)
    {
        $keys = array_keys($this->items);
        $results = array_map($callable, $this->items, $keys);

        return new self($results);
    }
public function map ( callable $ callable ) { $ keys = array_keys ( $ this -> items ) ; $ results = array_map ( $ callable , $ this -> items , $ keys ) ; return new self ( $ results ) ; }
Apply the callable to the collection items.

@param callable $callable

@return self
Apply the callable to the collection items .