jquery button using $.post()

I'm trying to use jquery to create a vote up, vote down button for my website. What i did was creating a form and have it processed in an external php script using $.post(). I thought this will allow the form to be processed in the quietly in the backend but when i click on the buttons, the jquery function doesn't seem to work and it just loads the whole script in the front-end.

Appreciate if anyone can provide some help here. Thanks. Following is my scripts.

Main PHP script

<div class="voting_class">
 
 <?php
     $user =& JFactory::getUser();
     $ip = getenv('REMOTE_ADDR');
     if($user->id == 185){
 ?>
 
 <form method="post" action="../vote_plus.php">
     <div class="form_element">
         <label>user_id</label>
         <input type="text" name="user_id" class="votetext" value="<?php echo $user->id;?>" />
     </div>
     <div class="element">
         <label>ad_id</label>
         <input type="text" name="ad_id" class="votetext" value="<?php echo $this->content->id;?>"/>
     </div>
     <div class="element">
         <label>ip_address</label>
         <input type="text" name="ip_address" class="votetext" value="<?php echo $ip;?>"/>
     </div>
     <div class="submit_element">
         <input type="submit" class="button" id="submitadd" value="Recommend"/>
         <div class="loading"></div>
     </div>
     <div class="submit_element">
         <input type="submit" class="button" id="submitminus" value="Don't Recommend" />
         <div class="loading"></div>
     </div>
 </form>
 <p class="success_msg" style="display:none"></p>
 
 <?php }?>
 
 </div>
 

JAVASCRIPT SCRIPT

<script type = "text/javascript">
 $(document).ready(function() {
 
     $('#submitadd').click(function(event) {       
 
     //Get the data from all the fields
     var user_id = $('input[name=user_id]');
     var ad_id = $('input[name=ad_id]');
     var ip_address = $('input[name=ip_address]');
 
     $.post('../vote_plus.php', { user: "user_id.val()", ad: "ad_id.val()", ip: "ip_address.val()" }, function () {
             $('.success_msg').append("Vote Successfully Recorded");
             $('.success_msg').fadeOut();
         });
         event.preventDefault();
     }); 
 });
     //if submit button is clicked
     $('#submitminus').click(function(event) {       
 
     //Get the data from all the fields
     var user_id = $('input[name=user_id]');
     var ad_id = $('input[name=ad_id]');
     var ip_address = $('input[name=ip_address]');
 
     $.post('../vote_minus.php', { user: "user_id.val()", ad: "ad_id.val()", ip: "ip_address.val()" }, function () {
             $('.success_msg').append("Vote Successfully Recorded");
             $('.success_msg').fadeOut();
         });
         event.preventDefault();
     });
 
 });
 </script>
 

I won't be posting the external script as i think the problem doesn't lie in the external php script as all mySQL updates can be loaded and properly and any info can be properly displayed. My problem lies where i can't get the button to work in jquery.

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