PHP-DI: create vs. autowire vs. get. Or how to correctly map an interface to an implementation provided by a definition

Question

For my PHP-DI container in a web MVC I prepared the following definition for a router:

return [
    'router' => function (ContainerInterface $c) {
        //...

        return new Router(...);
    }
];

Now I want to map an interface (MyLib\Routing\RouterInterface) to the implementation provided by the 'router' entry. In the PHP-DI documentation I found three ways of achieving this. Something like this:

1. RouterInterface::class => DI\create('router')
2. RouterInterface::class => DI\autowire('router')
3. RouterInterface::class => DI\get('router')

When I applied the 3rd option, all were ok, e.g. I could retrieve the interface entry with:

$router = $container->get(RouterInterface::class);
var_dump($router);

But, when I tried the first two options, I received the error:

(1/1) InvalidDefinition

Entry "MyLib\Routing\RouterInterface" cannot be resolved: the class doesn't exist
Full definition:
Object (
class = #UNKNOWN# router
lazy = false
)

So I'd like to ask: Could you please explain to me, what is the difference between the three options in this case?

Thank you

---

Completion to the accepted answer:

The answer of @MatthieuNapoli is correct. I would though complete it with the following conclusion - based on a test I ran (see bellow).

Conclusion:

The helper functions create() and autowire() do not, in any way, reference an entry in the container. They receive a class name as argument and make sure that an object of that class is NEWLY created (once). This happens even if the name of an existing container definition is identical with the class name, and even if that entry already creates an object of the same type.

Solely the helper function get() references container entries, and not class names (as Matthieu already kindly presented).

Test:

1) I defined the following class:

<?php

namespace Test;

class MyTestClass {

    public function __construct($input = NULL) {
        if (empty($input)) {
            $input = 'NO INPUT';
        }

        echo 'Hello from MyTestClass. Input is: ' . $input . '<br/>';
    }

}

2) I defined the following container entries:

return [
    'Test\MyTestClass' => function (ContainerInterface $c) {
        return new Test\MyTestClass('12345');
    },
    'my.test.entry.for.create' => DI\create('Test\MyTestClass'),
    'my.test.entry.for.autowire' => DI\autowire('Test\MyTestClass'),
    'my.test.entry.for.get' => DI\get('Test\MyTestClass'),
];

3) I executed the following code:

<?php

$myTestEntryFor_MyTestClass = $container->get('Test\MyTestClass');

$myTestEntryFor_Create = $container->get('my.test.entry.for.create');
$myTestEntryFor_Autowire = $container->get('my.test.entry.for.autowire');

/*
 * This prints nothing, because an object of type "MyTestClass" was
 * already created by the container definition "'Test\MyTestClass'".
 */
$myTestEntryFor_Get = $container->get('my.test.entry.for.get');

4) I received the following results:

Hello from MyTestClass. Input is: 12345
Hello from MyTestClass. Input is: NO INPUT
Hello from MyTestClass. Input is: NO INPUT

Answer 1

I invite you to check out the phpdoc of those functions in functions.php.

RouterInterface::class => DI\create('router')

That means create the router class: that PHP class doesn't exist.

RouterInterface::class => DI\autowire('router')

That means autowire the router class (which again doesn't exist).

RouterInterface::class => DI\get('router')

That means "when I ask for RouterInterface::class return the router entry. Notice that get() takes a container entry name, not a class name.