memcache 问题

$memcache_obj = new Memcache;
/* connect to memcached server */
$memcache_obj->connect('192.168.1.68',11211);$v = $memcache_obj->get('var_key');if(strlen($v)==0)
{
echo 'set...';
$memcache_obj->set('var_key', 'some really big variable', MEMCACHE_COMPRESSED, 0);
}
else
echo $memcache_obj->get('var_key');为社么一会显示"set...."一会 'some really big variable'set...的频率要高于'some really big variable' 求解谢谢！！