Bind vs Singleton in Laravel. Which one to use, and when?

In today’s tutorial, we are discussing bind() and singleton() methods in Laravel. In general, you might have encountered this a lot while you programming in Laravel based apps.

We use bind in the event of reusable classes or objects ( the object is created each time when it is called). So each instance of the class will be different from the previous one.

Imagine you need to display product details in your application, every product detail will be different, so as the every product object. You cannot use one instance for different products. So you will have to create a new instance for every new product.

We use singleton for a class or object when we need to access the same instance throughout the application( the object is constructed only once and keeps the state throughout the execution).

So when you need a single, shared instance of class you can use singleton.

For example, in a cache class, or in a log class, you don’t need to create different objects for this type of job. Instead of that, you use the same instance throughout the application.

We will examine this with the help of an example.

Create a class in the following path app\Support\TestClass.php

<?php
namespace App\Support;

class TestClass {

    protected $counter = 0;
    /**
     * Method increments the counter 
     */
    public function increment() {
        $this->counter++;
        return $this->counter;
    }
}

Open the AppServiceProvider.php file and add the below code to register() function.

App\Providers\AppServiceProvider.php

.......
public function register() {
    $this->app->singleton(
        'test1',
        \App\Support\TestClass::class
    );

    $this->app->bind(
        'test2',
        \App\Support\TestClass::class,
    );
}
......

Go to your console and type php artisan tinker. What is a tinker?. Laravel includes a powerful REPL, called Tinker, powered by the PsySH console by Justin Hileman under the hood. The tinker console allows you to interact with your Laravel application from the command line in an interactive shell.

And try to execute the classes in there

>>> app('test1')->increment()
=> 1
>>> app('test1')->increment()
=> 2
>>> app('test1')->increment()
=> 3
>>> app('test2')->increment()
=> 1
>>> app('test2')->increment()
=> 1
>>> app('test2')->increment()
=> 1
>>>

You can see test1 class is increments the counter, and what it means is it’s not creating a new instance every time, but it uses the same instance instead.  On the other hand, the test2 class creates a new object each time, so it prints the 1 always.

In addition, you can use the bind() as a singleton() if we set the third parameter is true, which is surprising in the first place, but it’s not. You will understand this better in a minute.

Consider this example with the third parameter as true

$this->app->bind(
    'test2',
    \App\Support\TestClass::class,
    true
);

We will execute the tinker again

Check the output below
>>> app('test2')->increment()
=> 1
>>> app('test2')->increment()
=> 2
>>> app('test2')->increment()
=> 3
>>> app('test2')->increment()
=> 4
>>>

Now it’s the same as the singleton() method. Basically, Laravel actually just proxies to call a bind(). For this reason, you are receiving the same results as a singleton().

To understand more, you can examine the below code from the core Laravel file.

\Illuminate\Container\Container in vendor/laravel/framework/src/Illuminate/Container/Container.php

public function singleton($abstract, $concrete = null)
{
    $this->bind($abstract, $concrete, true);
}

You can see that singleton() calls bind() but $shared= true

Tested in version – 8.7

Thanks to this article