Registry.php

<?php

class ClassRegistry {

    /**
     * @var array The store for all objects
     */
    private array $store = [];

    /**
     * Add an object to the registry
     *
     * If you do not specify a name the class name is used
     *
     * @param mixed $object The object to store
     * @param string $name Name used to retrieve the object
     * @return mixed If overwriting an object, old one is returned
     * @throws Exception
     * @TODO - Check Method and Param Type Declaration
     */
    public function add(object $object, string $name = null)
    {
        // Use the class name if not given, simulates singleton
        $name = (!is_null($name)) ? $name : get_class($object);
 // TODO return or not to return that is the question
        $return = null;
        if(isset($this->store[$name]))
        {
            $return = $this->store[$name];
        }

        $return = $this->store[$name] = $object;
        return $return;
    }

    /**
     * Get an object from the registry
     *
     * @param string $name Object name, {@see self::set()}
     * @return mixed
     * @throws Exception
     */
    public function get(string $name):object
    {
        if(!$this->contains($name))
        {
            throw new Exception("Object does not exist in registry");
        }
        return $this->store[$name];
    }

    /**
     * Check if an object is in the registry
     *
     * @param string $name Object name, {@see self::set()}
     * @return bool
     */
    static public function contains(string $name):bool
    {
        if(!isset($this->store[$name]))
        {
            return false;
        }

        return true;
    }

    /**
     * Remove an object from the registry
     *
     * @param string $name Object name, {@see self::set()}
     * @returns void
     */
    static public function remove(string $name):void
    {
        if($this->contains($name))
        {
            unset($this->store[$name]);
        }
    }
}

test.php