factory

<?php

function environment_factory($options) {
  $classes = array('provisionServer' => 'server_eval', 'provisionPlatform' => 'platform_eval', 'provisionSite' => 'site_eval');

  foreach ($classes as $class => $callback) {
    if ($callback($options)) {
      $className = $class; 
    }
    else {
      break;
    }
  }

  $object = new $className($options);
  return $object;
}

function server_eval($options) {
  return TRUE;
}


class provisionServer {
  function __construct($options) {
    $this->hostname = 'localhost';
  }
}


function platform_eval($options) {
  if ($options['root']) {
    return true;
  }
}

class provisionPlatform extends provisionServer {
  function __construct($options) {
    $this->root = $options['root'];
  }
}

function site_eval($options) {
  if ($options['uri']) {
    return true;
  }
}

class provisionSite extends provisionPlatform {
  function __construct($options) {
    parent::__construct($options);
    $this->uri = $options['uri'];
  }
}

print_r(environment_factory(array('root' => 1, 'uri' => 2)));