写了一个PHP MongoDB 的封装，经管已经有了不少轮子了

<?php

/**
 * Description of MongoUtil
 * MongoDB 封装类
 * 参考 PHP Manual<br/>
 * use like this:<br/>
 * $mongodb = MongoUtil::init();<br/>
 * $mongodb->find('collection_name');<br/>
 * @link http://www.php.net/manual/zh/book.mongo.php<br/>
 * @link http://docs.mongodb.org/manual/<br/>
 * 
 * @author Nomandia
 */
include_once __DIR__ . '/Config.php';

class MongoUtil {

    private static $instance;
    public $mongo;
    public $db_name;
    public $coll_name;
    public $cursor;

    public $auto_connect = true;
    public $errors;
    
    /**
     * 静态数据库
     */
    const DB_MODLUE = 'mp_module';
    /**
     * 用户数据库
     */
    const DB_USERDATA = 'mp_userdata';

    function __construct() {
        $config = Config::$MONGO_SERVER;
        shuffle($config['hosts']);
        $host = $config['hosts'][0];
//        echo 'mongodb://'.$host['ip'].':'.$host['port'].'/'.self::DB_USERDATA.'<br/>';
        try{
// 权限的部分暂时免了,根据需要写默认连接的数据库，否则就是self::DB_USERDATA
            $this->mongo = new MongoClient('mongodb://'.$host['ip'].':'.$host['port'].'/'.self::DB_USERDATA, array(connect=>$this->auto_connect));
        } catch(Exception $ex){
            $this->errors= $ex->getMessage();
        }
        $this->connect();
    }

    public static function init() {
        if (!self::$instance) {
            self::$instance = new MongoUtil();
        }
        return self::$instance;
    }

    public function __clone() {
        ;
    }
    
    public function __destruct() {
        $this->mongo->close();
    }

    // **************** 实例化后的方法 ****************
    public function connect() {
        return $this->mongo->connect();
    }

    public function select_db($db_name){
        $this->db_name = $db_name;
        try{
            return $this->mongo->selectDB($db_name);
        } catch (Exception $ex) {
            $this->errors = $ex->getMessage();
        }
    }
    
    public function list_db(){
        try{
            return $this->mongo->listDBs();
        } catch (Exception $ex) {
            $this->errors = $ex->getMessage();
        }
        return null;
    }
    
    /**
     * 获取一个MongoCollection对象
     * @param string 数据库名
     * @param string 集合名
     * @return MongoCollection MongoDB集合
     */
    public function select_collection($db_name, $coll_name){
        $this->db_name = $db_name;
        $this->coll_name = $coll_name;
        try {
            return $this->mongo->selectCollection($db_name, $coll_name);
        } catch (Exception $ex) {
            $this->errors = $ex->getMessage();
        }
    }
    
    /**
     * 删除集合
     * @param string 集合名
     * @return bool 操作结果
     */
    public function drop($coll_name){
        $db_name = $this->db_name;
        return $this->mongo->$db_name->$coll_name->drop();
    }

    /**
     * 创建一个索引
     * @param string 集合名
     * @param array 字段名
     * @param array array(unique=>false), unique=true时创建唯一索引
     * @return bool 操作结果
     */
    public function create_index($coll_name, $keys, $options=array(unique=>false)) {
        $db_name = $this->db_name;
        try{
            return $this->mongo->$db_name->$coll_name->createIndex($keys, $options);
        } catch (Exception $ex) {
            $this->errors = $ex->getMessage();
        }
        return false;
    }
    
    /**
     * 执行一条命令
     * @param array 命令
     * @return array 执行结果
     */
    public function command($coll_name, $command){
        $db_name = $this->db_name;
        return $this->mongo->$db_name->$coll_name->command($command);
    }
    
    /**
     * 删除集合索引
     * @param string 集合名
     * @param array 键
     * @return bool 操作结果
     */
    public function delete_index($coll_name, $keys){
        $db_name = $this->db_name;
        return $this->mongo->$db_name->$coll_name->deleteIndex($keys);
    }
    
    /**
     * 删除集合所有的索引
     * @param string 集合名
     * @return bool 操作结果
     */
    public function delete_all_index($coll_name){
        $db_name = $this->db_name;
        return $this->mongo->$db_name->$coll_name->deleteIndexes();
    }

    /**
     * 插入文档到集合（支持批量插入）
     * @param string 集合名
     * @param array 文档
     * @return bool 是否插入成功
     */
    public function insert($coll_name, $docs) {
        $db_name = $this->db_name;
        return $this->mongo->$db_name->$coll_name->insert($docs);
    }
    
    /**
     * 保存一个结果（如果存在此对象则更新，否则插入）
     * @param string 集合名
     * @param array 文档
     * @return bool 插入结果
     */
    public function save($coll_name, $neo_data){
        $db_name = $this->db_name;
        try{
            return $this->mongo->$db_name->$coll_name->save($neo_data);
        } catch (Exception $ex) {
            $this->errors = $ex->getMessage();
        }
        return false;
    }

    /**
     * 更新一个文档
     * @param string 集合名
     * @param array 条件
     * @param array 更新的文档
     * @param array 选项 array(upsert=>0) upsert=1时，如果不存在符合条件的文档则将新文档插入 multiple=1时表示更新所有符合条件的记录，否则只会更新1条
     * @return bool 是否插入成功
     */
    public function update($coll_name, $condition, $neo_data, $options = array(fsync=>0, upsert=>0, multiple=>0)) {
        $db_name = $this->db_name;
        $options['save'] = 1;
        if ( !isset($options['multiple'])){
            $options['multiple'] = 0;
        }
        try{
            return $this->mongo->$db_name->$coll_name->update($condition, $neo_data, $options);
        } catch (Exception $ex) {
            $this->errors = $ex->getMessage();
        }
        return false;
    }

    /**
     * 删除集合记录
     * @param string 集合名
     * @param array 删除条件
     * @param array 选项 array(justOne=>0) justOne=1时只删除1条记录
     * @return bool 删除结果
     */
    public function remove($coll_name, $condition, $options = array(justOne=>0, fsync=>0)) {
        $db_name = $this->db_name;
        $options['save'] = 1;
        if ( !isset($options['justOne'])){
            $options['justOne'] = 0;
        }
        try{
            return $this->mongo->$db_name->$coll_name->remove($condition, $options);
        } catch (Exception $ex) {
            $this->errors = $ex->getMessage();
        }
        return false;
    }

    /**
     * 查询MongoDB
     * @param string 集合名
     * @param array 查询的条件array<br/>如<i>array(col_a=>111)</i>
     * @param array 集合过滤器array<br/>完整的样子想这个：<i>array(sort=>array(col_a=>1,col_b=>-1), skip=>100, limit=>10, timeout=>5000, immortal=>true)</i>,这表示：
     * <ol>
     * <li>wrapped 以wrapped为封装为数组的键，默认按数组先后顺序</li>
     * <li>_id，默认不返回数据带有MongoID字段，如果指定了返回列的话也是一样的效果</li>
     * <li>sort 以col_a为ASC,col_b为DESC排序，可以多列组合</li>
     * <li>skip 表示从101条记录开始取数据，即跳过了前100条</li>
     * <li>limit 本次选取的条数</li>
     * <li>timeout 表示等待响应的时间（暂不使用）</li>
     * <li>immortal 表示是否维持链接永久有效，默认true，此时timeout失效（暂不使用）</li>
     * </ol>
     * @param array 需要返回的字段（通常只返回必要的字段可以加快响应速度）
     * @return mixed 查询的结果
     */
    public function find($coll_name, $condition=array(), $result_filter=array(wrapped=>'', with_objectId=>0, timeout=>5000, immortal=>true), $ret_fields = array() ) {
        $db_name = $this->db_name;
        $cursor = $this->mongo->$db_name->$coll_name->find($condition, $ret_fields);
        if ( !empty($result_filter['skip'])){
            $cursor->skip($result_filter['skip']);
        }
        if ( !empty($result_filter['limit'])){
            $cursor->limit($result_filter['limit']);
        }
        if ( !empty($result_filter['sort'])){
            $cursor->sort($result_filter['sort']);
        }
        if ( !empty($result_filter['wrapped'])){
            $wrapped = $result_filter['wrapped'];
        }
        if ( $result_filter['with_objectId']==1){ //如果指定了返回的列此项目就失效
            $with_objectId = count($ret_fields) < 1;
        }
        $result = array();
        $this->cursor = $cursor;
        try{
            if ( $wrapped == '_id'){
                while($ret = $cursor->getNext()){
                    $result[$ret['_id']->{'$id'}] = $ret;
                }
            } else if (strlen ($wrapped) ) {
                while($ret=$cursor->getNext()){
                    $result[$ret[$wrapped]] = $ret;
                }
            } else {
                while($ret=$cursor->getNext()){
                    $result[] = $ret;
                }
            }
            if ( !$with_objectId ){
                foreach($result as $key=>$v){
                    unset($result[$key]['_id']);
                }
            }
        } catch (Exception $ex) {
            $this->errors = $ex->getMessage();
        }
        return $result;
    }
    
    /**
     * 根据ID查询一条记录
     * @param string 集合名
     * @param string MongoId
     * @param mixed 指定返回的列，默认返回所有列
     * @return mixed 结果
     */
    public function find_by_objectId($coll_name, $_id, $ret_fields=array()){
        $db_name = $this->db_name;
        return $this->mongo->$db_name->$coll_name->findOne(array('_id'=>( new MongoId($_id))), $ret_fields);
    }

    /**
     * 查询一条记录
     * @param string 集合名
     * @param array 查询条件
     * @param array 需要返回的字段
     * @return array 查询的结果
     */
    public function find_one($coll_name, $condition=array(), $fields = array('_id'=>0)) {
        $db_name = $this->db_name;
        if ( is_string($condition['_id'])){
            $condition['_id'] = new MongoId($condition['_id']);
        }
        return $this->mongo->$db_name->$coll_name->findOne($condition, $fields);
    }
    
    /**
     * 计算集合内指定条件文档的数量
     * @param string 集合名
     * @param array 查询的条件
     * @param int 指定返回结果数量的上限
     * @param int 统计前跳过的结果数量
     * @return int 集合的数量
     */
    public function count($coll_name, $condition=array(), $limit=0, $skip=0){
        $db_name = $this->db_name;
        return $this->mongo->$db_name->$coll_name->count($condition, $limit, $skip);
    }
}

 或许你看到了Config.php，其实他貌似长成这个样子：

 <?php

final class Config {

    /**
     * Memcache 配置
     * @var mixed Memcache 配置
     */
    public static $MEMCACHE_SERVER = array(
        hosts => array(
            array(
                host => '127.0.0.1',
                port => 11211,
                weight => 100
            )
        ),
        threshold => 30000,
        saving => 0.2
    );

    /**
     * MongoDB 配置
     * @var mixed  MongoDB 配置 
     */
    public static $MONGO_SERVER = array(
        hosts => array(
            array(ip => '127.0.0.1', port => 27017, username => 'admin', password => 'admin', is_master => true)
//            ,array(ip => '127.0.0.1', port => 27018, username => 'admin', password => 'admin', is_master => true)
        )
    );

    /**
     * MySQL 配置
     * @var mixed MySQL 配置
     */
    public static $MYSQL_SERVER = array(
        host=>'127.0.0.1',
        user=>'root',
        password=>'123456',
        port=>3306
    );
}
?>