<?php

class Post {
  // ...
  public function create_action() {
    // ...
  }
  // ...
}


class FrontController {
  public function run() {
    @list($controller, $action, $param) = explode('/', $_SERVER['REQUEST_URI']);
    $controller = "${controller}Controller";
    $obj = new $controller();
    $method = "${action}_action";
    $obj->$method($param);
  }
}

$front = new FrontController();
$front->run();