On http://blog.caucho.com/?p=196, they have made Quercus run App Engine's datastore with PHP. Their source is at http://wordpress-on-quercus.appspot.com/wordpress-on-gae-quercus.zip
I would like to do something similar with their Google App Engine's memcache, preferably all in the PHP code since Quercus has the "import" command allowed within the PHP code.
I solved it.
<?php
import com.google.appengine.api.memcache.MemcacheService;
import com.google.appengine.api.memcache.MemcacheServiceFactory;
$service = MemcacheServiceFactory::getMemcacheService();
$service->put("key", "this is the value");
echo $service->get("key"); // outputs "this is the value"