PHP单例 - 这是对的吗？ [关闭]

Question

My code is below. Does it look right?

<?php

class goMongoDB
{
private static $Instance;

public function goMongoDB() {

    if ( !isset(self::$Instance) )
    {
        self::$Instance = new MongoClient();
    }
}

public function isConnected()
{
    return self::$Instance->connected;
}
}

$MongoClient = new goMongoDB();



print $MongoClient->isConnected();


?>

Answer 1

No, this is not a singleton implementation. Why? You can instantiate it as many as you want.

How to go about it?

1 - Prevent direct instantitation

private function __construct(){}

2 - Provide an instantiation mechanism

static function getInstance(){
   if ( !isset(self::$Instance) ){
       self::$Instance = new MongoClient();
    }
   return self::$Instance;
}

Now you can get your object like this:

$obj = goMongoDB::getInstance();

Be warned though that singletons can make debugging a real pain so use with care.

Hope this helps