Why am I getting PHP Fatal error: Uncaught Error: Class 'MyClass' not found?

Question

This works:

class MyClass {
    public $prop = 'hi';
}

class Container {
    static protected $registry = [];
    public static function get($key){
        if(!array_key_exists($key, static::$registry)){
            static::$registry[$key] = new $key;
        }
        return static::$registry[$key];
    }
}

$obj = Container::get('MyClass');
echo $obj->prop;

hi

But when I try to break it out into individual files, I get an error.

PHP Fatal error: Uncaught Error: Class 'MyClass' not found in /nstest/src/Container.php:9

This is line 9:

static::$registry[$key] = new $key;

What's crazy is that I can hard code it, and it works, so I know the namespace is correct.

static::$registry[$key] = new MyClass;

hi

Obviously I don't want to hard code it because I need dynamic values. I've also tried:

$key = $key::class;
static::$registry[$key] = new $key;

But that gives me this error:

PHP Fatal error: Dynamic class names are not allowed in compile-time ::class fetch

I'm at a loss. Clone these files to reproduce:

.
├── composer.json
├── main.php
├── src
│   ├── Container.php
│   └── MyClass.php
├── vendor
│   └── ...
└── works.php

Don't forget the autoloader.

composer dumpautoload

composer.json

{
    "autoload": {
        "psr-4": {
            "scratchers\\nstest\\": "src/"
        }
    }
}

main.php

require __DIR__.'/vendor/autoload.php';
use scratchers\nstest\Container;

$obj = Container::get('MyClass');
echo $obj->prop;

src/Container.php

namespace scratchers\nstest;

class Container {
    static protected $registry = [];
    public static function get($key){
        if(!array_key_exists($key, static::$registry)){
            static::$registry[$key] = new $key;
        }
        return static::$registry[$key];
    }
}

src/MyClass.php

namespace scratchers\nstest;

class MyClass {
    public $prop = 'hi';
}

Answer 1

Thanks to @tkausl, I was able to get around dynamic relative namespacing by passing the fully qualified name in as the variable.

require __DIR__.'/vendor/autoload.php';
use scratchers\nstest\Container;
use scratchers\nstest\MyClass;

$obj = Container::get(MyClass::class);
echo $obj->prop;

hi