chat session in chatbox in php

var lastTimeID = 0;

$(document).ready(function() {
  $('#btnSend').click( function() {
    sendChatText();
    $('#chatInput').val("");
  });
  startChat();
});

function startChat(){
  setInterval( function() { getChatText(); }, 2000);
}

function getChatText() {
  $.ajax({
    type: "GET",
    url: "/refresh.php?lastTimeID=" + lastTimeID
  }).done( function( data )
  {
    var jsonData = JSON.parse(data);
    var jsonLength = jsonData.results.length;
    var html = "";
    for (var i = 0; i < jsonLength; i++) {
      var result = jsonData.results[i];
      html += '<div style="color:#' + result.color + '">(' + result.chattime + ') <b>' + result.usrname +'</b>: ' + result.chattext + '</div>';
      lastTimeID = result.id;
    }
    $('#view_ajax').append(html);
  });
}

function sendChatText(){
  var chatInput = $('#chatInput').val();
  if(chatInput != ""){
    $.ajax({
      type: "GET",
      url: "/submit.php?chattext=" + encodeURIComponent( chatInput )
    });
  }
}
//Updates the chat
function updateChat(){
  $.ajax({

    type: "GET",
    url: "update.php",
    data: {  
        'state': state,
        'file' : file
        },
    dataType: "json",
    cache: false,
    success: function(data) {

        if (data.text != null) {
            for (var i = 0; i < data.text.length; i++) {  
            $('#chat-area').append($("<p>"+ data.text[i] +"</p>"));
        }

        document.getElementById('chat-area').scrollTop = document.getElementById('chat-area').scrollHeight;

    }  

    instanse = false;
    state = data.state;
    setTimeout('updateChat()', 1);

    },
  });
}