WeChat SDK by Zem is a third party kit that can help developers to integrate chat, messaging, video, and voice features into an app. This SDK works with PHP language. Particularly, WeChatClient assists to identify chat menu, manage groups, upload and download media files, and send server messages.
Nexmo offers a series of cloud-based communication APIs that make it easy to integrate reliable communication services into any application. This tutorial by Tim Lytle on the Nexmo blog shows followers how to build a simple text message group chat using the Nexmo SMS API and PHP.
Collaboration company 37Signals bought the popular Ember iPhone app, which uses the company's Campfire API (our Campfire API profile) to display and update chats. The app has been renamed 37Signals Campfire and is now available for free (previously $9.99).