Hi guys
A really short one today, just because someone asked me about it a couple of days ago. I also though it potentially best to avoid something as controversial as my last post about Eloquent and the Single Responsibility Principle, which caused a bit of a stir during the week.
So, you want to make sure you only ever use one specific instance of a class (maybe a DB connection) and need a quick and easy way to do it. Personally, this is the technique I would use:
<?php
class MySingleton{
// This will hold the instance of the class
private static $instance = null;
// Declare this as private to stop anybody being able to use the "new" keyword
private function __construct()
{
// Your usual constructor stuff in here
}
// This is where you get your instance
public static function getInstance()
{
if(is_null(self::$instance)){
self::$instance = new self();
}
return self::$instance;
}
}
All we’re doing here really, in a set of steps:
- You need a way to hold an instance of the object which is persistent throughout the execution
This is what the private static $instance is doing - You don’t want anybody to be able to directly use the new keyword, because then you’ve lost control of the instances of the object
- You need to be able to get an instance of the class, which is what the getInstance method is for
- In getInstance all we’re doing is instantiating the object if one hasn’t get been stored against the $instance static
So, to fetch your instance is simply:
$singleton = MySingleton::getInstance();
Wherever you run that throughout your code you will receive the exact same instance. Particularly useful in things like Database connections, loggers/debuggers and things like that.