Idea for a dependency injection service similar to Angular.js, but for handler function-based PHP routers like Slim Framework

Handler.php

<?php

/**
 * Class Handler
 *
 * Playing around with reflection & DI. Handler is a routing class (think Express [node.js] or Slim [php]),
 * with a built-in dependency injection system inspired by Angular.js.
 *
 * Consider this:
 *    - Use annotations in the handler callback to specify what class needs to be instantiated?
 *    - Use annotations to specify a 'key' that some DI framework that Handler bundles can use to build dep?
 *    - Depend solely on the arg name to match a class?
 *        - But what if a class is namespaced => \App\Service\User?
 */
class Handler {
   protected $inj = [];

   public function __construct() {
      $this->inj['time'] = function(){
         return time();
      };
   }

   public function doit($cb) {
      $ref = new ReflectionFunction($cb);
      $c = $ref->getParameters();

      // Fake deps resolution => if param name matches 'configured key' in $this->inj => build dep. Else, return as str
      $args = array_map(function($arg){
            $arg = $arg->name;
            if (array_key_exists($arg, $this->inj)) {
               return $this->inj[$arg]();
            } else {
               return $arg;
            }
      }, $c);

      return call_user_func_array($cb, $args);
   }
}

$h = new Handler();
$h->doit(function($time, $hello, $world){
      echo date('Y-m-d H:i:s', $time). ' ==> '. $hello. ', '. $world;
   }
);