print related detail using dynamically created select list - codeigniter

Question

I am coding a module in which i have to print the category.
For this firstly i had coded to filter on what basis you want to search (ID/ NAME) and then according to this information selected by user, a select list get created dynamically.
Here is the problem bit: this dynamically created select list, I want to print
it's related data (using where clause) in form field. I'm not getting the field's echo. The rest part (dynamic select list box) is appearing;
Here is my view:
<div class="navbar">
<div class="navbar-inner">
<h2>Show Category</h2>
<?php
$dropdown_category= array(
'c_id'=>'Category Code',
'c_name'=>'Category Name');
echo form_dropdown('clas',$dropdown_category,'','id="clas"');
?>
<div id="name_sec">
<!-- PRONT DROP DOWN HERE !-->
</div>
</div>
<br/>
<div class="navbar-inner">
<br/>
<div id="name_sec2">
<!-- PRONT form fields HERE !-->
</div>
</div>
<div class="navbar"></div>
</div>
My controller :
public function category_display()
{
//Checking so that people cannot go to the page directly.
$this->load->helper('form');
$this->load->database();
$tabel_for_this="its_category";
$data_toprint='';
$id=$this->input->post('send_data_post');
$query = $this->db->query("SELECT ".$id." FROM ".$tabel_for_this." ");
foreach ($query->result_array() as $r)
{
$dropdown_category2[$r[$id]] = $r[$id];
}
echo form_dropdown('clas2',$dropdown_category2,'','id="clas2"');
}
public function category_display_in_fields()
{
$this->load->helper('form');
$this->load->database();
$tabel_for_this="its_category";
$data_toprint='';
$id=$this->input->post('send_data_post_for_field');
$sql = "SELECT * FROM ".$tabel_for_this." where '".$id."'= ?";
$query = $this->db->query($sql,$id);
foreach ($query->result_array() as $r)
{
echo '<input type="text" name="c_dateadded" placeholder="Date" value>
<input type="text" name="'.$r['c_id'].'" placeholder="'.$r['c_name'].'" value>
<select name="c_addedby" placeholder="Added By" value>
<option>added by</option><option>name1</option><option>name2</option><option>name3</option><option>name4</option>
</select>
<input type="text" name="c_description" placeholder="Description" value>
<input type="text" name="i_nos." placeholder="Total Items No." value>
<input type="text" name="c_i_nos_avail" placeholder="Available Stock" value> ';
}
}
here is my js :
<script type="text/javascript" src="http://code.jquery.com/jquery-1.6.4.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$("#clas").change(function(){
var send_data=$("#clas").val();
$.ajax({
type:"post",
url:"category_display",
data:"send_data_post="+send_data,
success:function(data){
$("#name_sec").html(data);
}
});
});
});
</script>
<!-- CODE TO PRINT DATA IN FIELDS!-->
<script type="text/javascript">
$(document).ready(function(){
$("#clas2").change(function(){
var send_data2=$("#clas2").val();
$.ajax({
type:"post",
url:"category_display_in_fields",
data:"send_data_post_for_field="+send_data2,
success:function(data2){
$("#name_sec2").html(data2);
}
});
});
});
</script>
JUST FOR TESTING PURPOSE I HAVE CODED DATABASE RELATED THING IN CONTROLLER

Answer 1

Both the column and the variable in your where clause are the same:
$id=$this->input->post('send_data_post_for_field');
$sql = "SELECT * FROM ".$tabel_for_this." where '".$id."'= ?";
$query = $this->db->query($sql,$id);
So the returning query will do something like this:
SELECT * FROM table WHERE var = var
Which is wrong.
It should be something like this:
$sql = "SELECT * FROM ".$tabel_for_this." where id= ?";