data are not saving in mysql using php

I have php page to enter some details of audit and finally save in database.But when i entered the data,and press the save button.But it doesn't get saved in database.When i use error_log() function to check whether php function is working or not as below, in my log file only "Started" is there.. their is no "submitted" and further database error message.

Note: im new to php,started to develop php application using xampp and notepad++

auditentry.php

 <?php
    include("config.php"); 
    include("header.php"); 
    session_start();
    error_log("started");
    ?>

<link href="<?=BASE_URL?>bootstrap/css/bootstrap.css" rel="stylesheet"> 
<link rel="stylesheet" href="<?=BASE_URL?>/bootstrap/css/bootstrap.min.css">
 <script type="text/javascript" src="<?=BASE_URL?>js/jquery.js"></script> 
<script src="<?=BASE_URL?>bootstrap/js/bootstrap.js"></script>  
 <link href="<?=BASE_URL?>bootstrap/css/bootstrap-responsive.css" rel="stylesheet">

<div class="col-md-10 main">     

<h1 class="page-header">
   Audit Plan  Entry          
 </h1>      
     <form class="form-horizontal" role="form">
    <div class="form-group">
      <label class="control-label col-sm-2" for="usr">Audit ID:</label>  
        <div class="col-sm-5"> 
          <input  type="text" class="form-control" id="auditid" name ="auditid" placeholder="Eg: IA01">
        </div>
    </div>
    <div class="form-group">
      <label class="control-label col-sm-2" for="pwd">Year:</label>
        <div class="col-sm-5">
            <input type="text" class="form-control col-xs-3" id="year" name ="year">
        </div>
    </div>
    <div class="form-group">
      <label class="control-label col-sm-2" for="usr">Month:</label>
        <div class="col-sm-5">
            <input  type="text" class="form-control" id="month" name ="month">
        </div>
    </div>
     <div class="form-group">
      <label class="control-label col-sm-2 " for="sel1">Status:</label>
        <div class="col-sm-5">
          <select class="form-control" id="sel1" name="status">
            <option>Planned</option>
            <option>Scheduled</option>
            <option>Completed</option>
            <option>Cancelled</option>
          </select>
        </div>
    </div>

     <div class="form-group">
      <label class="control-label col-sm-2" for="comment">Comment:</label>
        <div class="col-sm-5">
            <textarea class="form-control" rows="3" id="comment" name="comment"></textarea>
        </div>
    </div>  

    <div class="form-group">        
          <div class=" col-sm-offset-3">
            <button type="submit" name="submit" id ="submit" class="btn btn-primary">Save</button>
            <button type="reset" name="submit1" id ="clear" class="btn btn-primary">Cancel</button>
          </div>

     </div>     
    </form>           
    </div>

    <?php
        if(isset($_POST['submit']))
            { 
        error_log("Submitted");
                    if(trim($_POST['auditid'])=='')
                        {
                echo "<script language='javascript'>alert('Please Enter Audit ID.');</script>";
                exit;
                        }                   
                elseif(trim($_POST['year'])=='')
                        {
                echo "<script language='javascript'>alert('Please Enter Year.');</script>";
                exit;
                        }
                elseif(trim($_POST['month'])=='')
                        {
                echo "<script language='javascript'>alert('Please Enter Month.');</script>";
                exit;
                        }
                elseif(trim($_POST['Status'])=='None')
                        {
                echo "<script language='javascript'>alert('Please Enter Status.');</script>";
                exit;
                        }
                $audit=trim($_REQUEST['auditid']);
                $year=trim($_REQUEST['year']);
                $month=trim($_REQUEST['month']);        
                $status =$_REQUEST['status'];
                $comment=$_REQUEST['comment'];  

                error_log($audit);


            $con = mysql_connect("localhost","root","") or die("Sorry you are not connected to server. Try Again!");
             mysql_select_db("simauditdb", $con) or die ("Cannot connect to database.");


            $insert=  "insert into auditplan 
            values('','$audit','$year','$month','$status','$comment','1')"; 

            error_log($insert);

                $result=mysql_query($insert) or die('Connection Failed'.mysql_error());
                echo "<script language='javascript'>alert('Audit Details Entered Successfully');</script>";     

                mysql_close($con); 

            }
        elseif(isset($_POST['submit1']))
                {
                echo "<script language='javascript'>document.location.href='Auditplan.php';</script>";
                }           
    ?>