我想通过jaxl.v3开发与facebook的聊天。这是我的代码`$client->add_cb('on_chat_message',function($stanza){global$client;//echobackincomingmessagestanza$stanza->to=$stanza->from;$stanza->from=$client->full_jid->to_string();print_r($stanza);sendMessage($client);});`这是我打印print_r($stanza)的结果:我现在问什么:如果我想获得[text]=>hi值。我应该