Question

I would like to ask about the performance and memory usage of instantiating an object in php.

On every php file of my application, i included a file which connect to the database.

$db->DB::getInstance();
$db->connect('all my credentials');

This is the getInstance() function in my db class.

//singleton database instance
public static function getInstance() {
    if (!self::$Instance) {
        self::$Instance = new DB();
    }

    return self::$Instance;
}

Currently everything turns out well. But i am concern of performance issues as in, can it be improved, possbile flaws etc.

I researched and found out that singleton instance can help to save memory. It will reuse the object if it’s already been instantiate. Am i right?

My exact question is

E.g. if i have 10 users accessing the script, does it means that the object will be instantiate 10 times? When that happens, will it put 10 x load on my memory usage? -> this is pretty what i am interested in

Appreciate any expert advice.

Answer 1

As with all performance tweaking, you should measure what you’re doing instead of just blindly performing some voodoo rituals that you don’t fully understand. When you save an object in $_SESSION, PHP will capture the objects state and generate a file from it (serialization). Upon the next request, PHP will then create a new object and re-populate it with this state. This process is much more expensive than just creating the object, since PHP will have to make disk I/O and then parse the serialized data. This has to happen both on read and write.

In general, PHP is designed as a shared-nothing architecture. This has its pros and its cons, but trying to somehow sidestep it, is usually not a very good idea.