Save documents into Mongodb collection with autoincrement field

CustomMongoCollection.php

<?php
/**
 * @Author Dmitry Kazberovich
 */

class CustomMongoCollection extends MongoCollection
{
    private $_autoincrementFieldName;

    public function __construct($db, $collectionName, $autoincrementFieldName = '')
    {
        $this->_autoincrementFieldName = $autoincrementFieldName;
        return parent::__construct($db, $collectionName);
    }

    public function insert($document, $options = array())
    {
        $document = (object) $document;
        if (!empty($this->_autoincrementFieldName)) {
            $this->saveWithAutoincrement($document, $options, 'insert');
        } else {
            return parent::insert($document, $options);
        }
    }

    public function save($document, $options = array())
    {
        $document = (object) $document;
        if (!empty($this->_autoincrementFieldName) && empty($document->{$this->_autoincrementFieldName})) {
            $this->saveWithAutoincrement($document, $options, 'save');
        } else {
            return parent::save($document, $options);
        }
    }

    protected function saveWithAutoincrement($document, $options, $operation = 'save')
    {
        while (1) {
            $mongoCursor = $this->find(array(), array($this->_autoincrementFieldName))
              ->sort(array($this->_autoincrementFieldName => -1))
              ->limit(1);

            if ($mongoCursor->hasNext()) {
                $mongoCursor->next();
                $doc = $mongoCursor->current();
                $document->{$this->_autoincrementFieldName} = ++$doc[$this->_autoincrementFieldName];
            } else {
                $document->{$this->_autoincrementFieldName} = 1;
            }

            try {
                return parent::$operation($document, $options);
            } catch (MongoCursorException $e) {
                if ($e->getCode() == '11000') //Duplicate key
                {
                    continue;
                } else {
                    throw $e;
                }
            }
        }
    }
}