<form action="<?php echo base_url();?>site/search/" method="POST">
    <input type="text" name="search_terms" placeholder="POST Search..." />
    <input type="submit" value="Search" />
</form>

 
<hr />
 
<input type="text" name="search" id="search_terms" placeholder="AJAX Search..." />
<input type="button" value="Search" id="do_search" />
 
<div id="search_results">
</div>
 
<script src="http://code.jquery.com/jquery-1.11.1.min.js"></script>
<script src="<?php echo base_url();?>assets/js/ItemSearch.js"></script>
<script src="<?php echo base_url();?>assets/js/site.js"></script>