FluentDOM\Query::content PHP Method

    private function content($content, callable $export, callable $import, callable $insert)
    {
        if (isset($content)) {
            $callback = Constraints::isCallable($content, FALSE, TRUE);
            if ($callback) {
                foreach ($this->_nodes as $index => $node) {
                    $contentString = $callback($node, $index, $export($node));
                    $insert($node, $import($contentString));
                }
            } else {
                $fragment = $import($content);
                foreach ($this->_nodes as $node) {
                    $insert($node, $fragment);
                }
            }
            return $this;
        } elseif (isset($this->_nodes[0])) {
            return $export($this->_nodes[0]);
        }
        return '';
    }