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Live Comment System with jQuery Ajax PHP and MySQL

Recently I have been made a post that focused on how to submit form without page refreshing. That post shows the basic functionality of using jQuery Ajax. On the same follow this post will describe how we can create a comment system to post an instant comment without page refreshing. Let's start...

Demo Download Source
Database Design
We need to create two database table post and comment.

Post Table
The post table holds post data like post id, title, body or whatever you want. You need to inset some table rows. You will find it on demo.sql file.
  `post_id` int(8) NOT NULL AUTO_INCREMENT,
  `post_title` varchar(124) NOT NULL,
  `post_body` text NOT NULL,
  PRIMARY KEY (`post_id`)
Comment Table
The comment table holds comment information. Here I only store commenter's name, mail and comment. If you want you can store more information like ip address, url or whatever you. Another thing you must to do, that to include is post id. It will tell you this comment is for which post.
CREATE TABLE `comment` (
  `name` varchar(128) NOT NULL,
  `mail` varchar(128) NOT NULL,
  `comment` text NOT NULL,
  `post_id` int(8) NOT NULL,
  PRIMARY KEY (`id`)
HTML Markup
This html code holds simple single post information. Post data will be placed in and comments will be place in div.comment-block. We also need to add a comment form. I used here some html5 form properties, attributes and form validations like type="email", placeholder and required.
  <title>Comment System</title>
  <div class="post">
    <!-- post will be placed here from db -->
  <div class="comment-block">
    <!-- comment will be apped here from db-->
  <!-- comment form -->
  <form id="form" method="post">
    <!-- need to supply post id with hidden fild -->
    <input type="hidden" name="postid" value="1">
      <span>Name *</span>
      <input type="text" name="name" id="comment-name" placeholder="Your name here...." required>
      <span>Email *</span>
      <input type="email" name="mail" id="comment-mail" placeholder="Your mail here...." required>
      <span>Your comment *</span>
      <textarea name="comment" id="comment" cols="30" rows="10" placeholder="Type your comment here...." required></textarea>
    <input type="submit" id="submit" value="Submit Comment">
JavaScript Code
This jQuery code is based on jQuery form submit event. When form submitted by user it sends a asynchronous request using jQuery.ajax method.
<script src=""></script>
  var form = $('form');
  var submit = $('#submit');

  form.on('submit', function(e) {
    // prevent default action
    // send ajax request
      url: 'ajax_comment.php',
      type: 'POST',
      cache: false,
      data: form.serialize(), //form serizlize data
      beforeSend: function(){
        // change submit button value text and disabled it
        submit.val('Submitting...').attr('disabled', 'disabled');
      success: function(data){
        // Append with fadeIn see
        var item = $(data).hide().fadeIn(800);

        // reset form and button
        submit.val('Submit Comment').removeAttr('disabled');
      error: function(e){
PHP Code
ajax_comment.php file holds this code. When the JavaScript sends asynchronous request this file receives serialized data and inserts into comment table. It also print out new comment for Ajax callback. Note, I haven't used any form validation code here. If you want to use it in real life project you must need to add form validation code.
// code will run if request through ajax
if (isset( $_SERVER['HTTP_X_REQUESTED_WITH'] )):
  // connecting to db
  if (!empty($_POST['name']) AND !empty($_POST['mail']) AND !empty($_POST['comment']) AND !empty($_POST['postid'])) {
    // preventing sql injection
    $name = mysql_real_escape_string($_POST['name']);
    $mail = mysql_real_escape_string($_POST['mail']);
    $comment = mysql_real_escape_string($_POST['comment']);
    $postId = mysql_real_escape_string($_POST['postid']);

    // insert new comment into comment table
      INSERT INTO comment
      (name, mail, comment, post_id)
      VALUES('{$name}', '{$mail}', '{$comment}', '{$postId}')");  
<!-- sending response with new comment and html markup-->
<div class="comment-item">
  <div class="comment-avatar">
    <img src="<?php echo avatar($mail) ?>" alt="avatar">
  <div class="comment-post">
    <h3><?php echo $name ?> <span>said....</span></h3>
    <p><?php echo $comment?></p>

  // close connection

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