Extending CController with support for action-method argument resolvers.

Controller.php

<?php

class Controller extends CController
{
  /**
   * @var array A stack of action-method arguments resolved by calls to resolve() from beforeAction().
   */
  protected $resolved = array();

  /**
   * Resolves parameter-names (e.g. $_GET[] variables) as action-method arguments.
   *
   * Call this from within your Controller's beforeAction() method, typically to convert IDs to objects.
   *
   * @param string $param_name name of the input $_GET[] variable to resolve - typically something that ends in "_id".
   * @param string $argument_name the name of the resolved action-method argument; defaults to $param_name without the "_id" suffix.
   * @param string|array|callable $fn a Controller method-name, an anonymous function/closure, or a callback-array.
   * @throws CException if the specified resolver-function could not be called.
   */
  protected function resolve($param_name, $argument_name=null, $fn=null)
  {
    if (!array_key_exists($param_name, $_GET)) {
      return; // no $_GET[] variable input - nothing to resolve.
    }

    if ($argument_name === null) {
      // Establish argument-name based on parameter-name - e.g. "document" for "document_id"
      if (substr_compare($param_name, '_id', -3) === 0) {
        $argument_name = substr($param_name, 0, -3);
      } else {
        throw new CException("argument-name could not be inferred from parameter-name"
                               . " - use parameter-names ending in '_id', or specify the argument-name");
      }
    }

    if ($fn === null) {
      // Establish method-name based on parameter-name, e.g. resolveDocumentId() for "document_id".
      $fn = 'resolve' . str_replace(' ', '', ucwords(str_replace('_', ' ', $param_name)));
    }

    $callback = $fn;

    if (is_string($callback)) {
      // Assume a method-name:
      $callback = array($this, $fn);
    }

    if (is_callable($callback) === false) {
      throw new CException("invalid resolver function: ".print_r($fn, true));
    }

    $this->resolved[ count($this->resolved)-1 ][$argument_name] = call_user_func($callback, $_GET[$param_name]);
  }  
  
  /**
   * Runs the action after passing through all filters.
   *
   * @param CAction $action action to run
   */
  public function runAction($action)
  {
    $this->resolved[] = array();

    parent::runAction($action);

    array_pop($this->resolved);
  }

  /**
   * Returns the request parameters that will be used for action parameter binding.
   *
   * @return array the request parameters to be used for action parameter binding.
   * @throws CException for internal errors only.
   */
  public function getActionParams()
  {
    $resolved = end($this->resolved);

    if (!is_array($resolved)) {
      throw new CException("internal error: resolve() should be called from inside your beforeAction() method only");
    }

    return array_merge($_GET, $resolved);
  }
}