MongoDB adapter for Code igniter 2

Mongo_model.php

<?php
/*
*   1. Add this file to libraries folder
*   2. Extend the Mongo_model class in your models (models directory) example: class User_model extends Mongo_model
*   3. add protected statis $collectionName = 'here the name of your mongo collection';
*   4. Load it in your controller, example:	Mongo_model::load('user_model');
*/
class Mongo_Model
{
    protected static $collectionName;
    protected $collection;
    protected $CI;

    private $new_instance = true;
    private $primary_key = null;

    public function __construct(){
        $this->CI = & get_instance();
        $this->collection =  SELF::getCollection();
    }


    /**
     * @param $mixWhere array|string mongoID
     * @param array $select
     * @return array of objects|single object => Depending of the count
     */
    static public function find($mixWhere = [] , $select = []){

        $collection =   SELF::getCollection();
        $where = [];
        if(is_array($mixWhere))
            $where = $mixWhere;
        else
            $where = ['_id' => new MongoId($mixWhere)];

        $cursor = $collection->find($where, $select);

        $return = null;
        if($cursor->count() == 1){
            $data = @reset(iterator_to_array($cursor));

            $return = new static();
            $return->setNewInstance(false);
            $return->setPrimaryKey($where);

            foreach($data as $name => $value)
                $return->{$name} = $value;
        }else if($cursor->count() > 1){

            foreach($cursor as $obj){
                $tmp = new static();
                $tmp->setNewInstance(false);
                $tmp->setPrimaryKey(['_id' => $obj['_id']]);

                foreach($obj as $name => $value)
                    $tmp->{$name} = $value;

                $return[] = $obj;
            }
        }
        return $return;
    }

    public static function exists($mixWhere){
        $collection =  SELF::getCollection();
        $where = [];
        if(is_array($mixWhere))
            $where = $mixWhere;
        else
            $where = ['_id' => new MongoId($mixWhere)];

        return $collection->count($where);
    }


    public function save($operators = []){
        $prop = $this->getPublicProperties();

        //##INSERT
        if($this->new_instance == true){
            try{
                $this->collection->insert($prop);
                $this->_id = $prop['_id'];
                $this->setPrimaryKey(['_id' => $this->_id]);
                $this->setNewInstance(false);
                return true;
            }catch (Exception $e){return false;}
        //##UPDATE
        }else{
            if(!empty($operators))
                $prop = $operators;

            $this->collection->update($this->primary_key, $prop);
            return true;
        }
    }

    public static function update($where, $update, $options = []){
         $collection =  SELF::getCollection();
         return $collection->update($where, $update, $options);
    }

    public function getId(){
        if(isset($this->_id) && gettype($this->_id) == 'object'){
            return $this->_id->{'$id'};
        }
        return '';
    }

    public function remove(){
        if(!empty($this->primary_key)){
            $this->collection->remove($this->primary_key);
            return true;
        }
        return false;
    }

    public static function delete($mixWhere){
        $where = [];
        if(is_array($mixWhere))
            $where = $mixWhere;
        else
            $where = ['_id' => new MongoId($mixWhere)];

        SELF::getCollection()->remove($where);
       
        return true;
    }

    public function setNewInstance($bool){
        $this->new_instance = $bool;
    }

    public function setPrimaryKey($mix){
        $this->primary_key = $mix;
    }

    private function getPublicProperties($notID = false){
        $public_properties = (new ReflectionObject($this))->getProperties(ReflectionProperty::IS_PUBLIC);
        $properties = [];
        foreach($public_properties as $key => $property){
            if($property->name != "_id" || $notID)
                $properties[$property->name] = $this->{$property->name};
        }
        return $properties;
    }

    private static function getCollection(){
        $CI = & get_instance();
        return $CI->mongo_db->db->selectCollection(static::$collectionName);
    }

    /*
     * load($file_name) loads mongo models
     * @param: $file_name => Name of the file in /models directory
     *
     */
    public static function load($file_name){
        //File name must match because linux is case sensitive
        require_once APPPATH."models/".ucfirst($file_name).".php";
    }
}