Use variable in php comment

As LazyOne said in the comments already PHP interfaces should solve your problem. You can 't use variables in PHPDoc formatted comments. Sure, if you use an IDE like PHPStorm with a plugin that enables the usage of variables in PHPDoc comments, the problem is solved for yourself. What, when other developers, which don 't use PHPStorm or the relevant plugin, want to work in the same project? In my view you should use php native functionality to solve your issue.

Here 's a short example how to use interfaces.

declare('strict_types=1');
namespace Application\Model;

interface ModelInterface
{
    public function getFoo() : string;

    public function setFoo() : ModelInterface;
}

The only thing you have to do now is using this interface with your models like in the following example.

declare('strict_types=1');
namespace Application\Model;

class FooModel implements ModelInterface
{
    protected $foo = '';

    public function getFoo() : string
    {
        return $this->foo;
    }

    public function setFoo(string $foo) : ModelInterface
    {
        $this->foo = $foo;
        return $this;
    }
}

As you can see the FooModel class implements the ModelInterface interface. So you have to use the methods declared in the interface in you model class. This means, that your getService Method could look like the following example.

/**
 * Some getter function to get a model
 * @return \Application\Model\ModelInterface
 */
public function getService($service) : ModelInterface
{
    return $service->get(\Application\Model\Foo::class);
}

Your IDE knows now which methods the returned class can use. It allows you to use chaining and some more features. While typing your IDE should know now, that the returned class can use getFoo and setFoo methods. Further the setFoo methods enables comfortable chaining for calls like ..

// variable contains the string 'foo'
// your ide knows all methods
$fooString = $this->getService($serviceLocator)->setFoo('foo')->getFoo();

Are you using Symfony? Then you could use the Symfony plugin that solves this problem for you. For other frameworks, there should be similar solutions. If you use your own framework, you need to write such a plugin on your own, as PhpStorm can not resolve the given class otherwise.

I think what you are looking for is phpdoc.

https://docs.phpdoc.org/guides/docblocks.html

/**
 * @param string $Service This is the description.
 * @return \Panel\Model\{$Service}
 */ 
public function getService($Service){
    // I call service `foo` from Model folder
}