The following code can be used to add embed chatroom into a PHP page:
<style>
.drupalchat-embed-chatroom-content {height: 550px !important;}
</style>
<script type="text/javascript">
if(typeof iflyembed == "undefined") {
iflyembed = {};
iflyembed.settings = {};
iflyembed.settings.ifly = {};
}
iflyembed.settings.ifly.embed = "1";
iflyembed.settings.ifly.ur_hy = "1";
iflyembed.settings.ifly.embed_msg = 'Type your message here. Press Enter to send.';
iflyembed.settings.ifly.embed_online_user_text = 'Online Users';
</script>
</script>
<div id="drupalchat-embed-chatroom-0" class="drupalchat-embed-chatroom-container"></div>
Paste the above code as HTML in your PHP page.