How to add comments live using ajax?

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Javascript

PHP

Ajax

jQuery

Below is a php code for inserting comment to a post, It works fine now I want to add ajax code to add comments live (without page being refreshed). I prefer ajax code and php code on same page because code will be carrying id's of users so don't want to send such data to another page through ajax/js. I am not good at programming tried few ajax codes but failed so if anyone can help me with ajax code will be thankful.

<?php
   if(isset($_POST['submit'])) {
     $comment=strip_tags($_POST['content']);
     $com = $db->prepare("INSERT INTO comments (comment,userto, userfrom, blog) VALUES (:comment, :userto, :userfrom, :blog)");
     $com->execute(array(':comment'=>$comment,':userto'=>$userid,':userfrom'=>$uid,':blog'=>$blogId));

   }
?>

<form method='post' name='form' action='' class='commentbox2'>
<textarea  name='content' id='content'></textarea><br />
<input type='submit' value='Comment' name='submit' class='comment_button'/>
</form>