I have this working code that is written in plain php (Meaning no framework). I would like to implement it to codeigniter, but I don't have any idea.

The purpose of this code is: When a user selects a category from dropdown, it show extra fields at the bottom. EX If a user selects Real-estate the following fields appears; capacity (input text), rooms(select), furnished(select, yes/no).

Ok, the main point is instead of using Show/Hide which requires a bench of html I just get all that from database.

This is my functions.php

PHP Code:
 function get_form_names($id) {

    
$database = new Database();

    
$database->query("SELECT * FROM field WHERE id_cat = :id");

    
$database->bind(':id',$id);

    
$database->execute();

    
$rows $database->resultset();

    return 
$rows;

  }


  function 
get_form_value($id) {

   
$database = new Database();

   
$database->query("SELECT * FROM value WHERE energy = :id ");

   
$database->bind(':id',$id);

   
$database->execute();

   
$rows $database->resultset();

  return 
$rows;

 }


 function 
display_form($array) {

  foreach(
$array as $key=>$valuee) {
    
$form_value get_form_value(htmlentities($valuee['select'],ENT_QUOTES));
    
$id htmlentities($valuee['id'], ENT_QUOTES);
    
$form_name "form".$id;
    if( !empty(
$_SESSION[$form_name]) ) {
        
$value =htmlentities($_SESSION[$form_name], ENT_QUOTES'utf-8');
        
$value stripslashes($value);
    }else {
        
$value " ";
    }
    echo
" <tr>
         <td width=\"200\" valign=\"top\" height=\"30\"  >
         <div style=\"padding-top: 3px;text-align:right; \">"
;
    echo 
"<span\"> ".htmlentities($valuee['disp_name'],ENT_QUOTES'utf-8')." :</span>";
    echo
"</div>
         </td>
         <td width=\"540\" valign=\"top\" height=\"30\">
         <div style=\"padding-left: 10px;\">"
;
    if(
htmlentities($valuee['type'], ENT_QUOTES) == 'txt') {
        echo
"
        <input type=\"text\" name=\""
.$form_name."\"";
        if( !empty(
$value) && $value != " " ) {
            echo 
"value=\"".$value."\">&nbsp;".htmlentities($valuee['unit'], ENT_QUOTES,  
        
'utf-8')."";
        }else {
        echo 
" value=\"\">&nbsp;".htmlentities($valuee['unit'], ENT_QUOTES'utf-
        8'
)."&nbsp;&nbsp;";
        }
    }elseif(
htmlentities($valuee['type'], ENT_QUOTES) == 'sel') {
        echo
"
        <select name=\" "
.$form_name."\">";
        if(
is_array($form_value)) {
            foreach(
$form_value as $v=>$vv) {
                if(empty(
$confirm)) {
                    
$value htmlentities($vv['select'], ENT_QUOTES'utf-8');
                }else {
                    
$value htmlentities($_SESSION[$form_name]);
                }
                echo 
"<option value=\"".$value."\" >".$value."</option>";
            }
        }
        echo
"</select>
            "
;
    }
    echo 
"
            </div>
            </td>
            </tr>"
;

 }

foreach($array as $key=>$valuee) {
$form_value = get_form_value(htmlentities($valuee['select'],ENT_QUOTES));
$id = htmlentities($valuee['id'], ENT_QUOTES);
$form_name = "form".$id;
if( !empty($_SESSION[$form_name]) ) {
$value =htmlentities($_SESSION[$form_name], ENT_QUOTES, 'utf-8');
$value = stripslashes($value);
}else {
$value = " ";
}
echo" <tr>
<td width=\"200\" valign=\"top\" height=\"30\" >
<div style=\"padding-top: 3px;text-align:right; \">";
echo "<span\"> ".htmlentities($valuee['disp_name'],ENT_QUOTES, 'utf-8')." :</span>";
echo"</div>
</td>
<td width=\"540\" valign=\"top\" height=\"30\">
<div style=\"padding-left: 10px;\">";
if(htmlentities($valuee['type'], ENT_QUOTES) == 'txt') {
echo"
<input type=\"text\" name=\"".$form_name."\"";
if( !empty($value) && $value != " " ) {
echo "value=\"".$value."\">&nbsp;".htmlentities($valuee['unit'], ENT_QUOTES,
'utf-8')."";
}else {
echo " value=\"\">&nbsp;".htmlentities($valuee['unit'], ENT_QUOTES, 'utf-
8')."&nbsp;&nbsp;";
}
}elseif(htmlentities($valuee['type'], ENT_QUOTES) == 'sel') {
echo"
<select name=\" ".$form_name."\">";
if(is_array($form_value)) {
foreach($form_value as $v=>$vv) {
if(empty($confirm)) {
$value = htmlentities($vv['select'], ENT_QUOTES, 'utf-8');
}else {
$value = htmlentities($_SESSION[$form_name]);
}
echo "<option value=\"".$value."\" >".$value."</option>";
}
}
echo"</select>
";
}
echo "
</div>
</td>
</tr>";

}
}

And this is the insert.php page


PHP Code:
if( isset($_POST['cat']) )
{
$cat = (int) $_POST['cat'];
}   
elseif( !empty(
$_SESSION['cat']) )
{
$cat = (int) $_SESSION['cat'];
}else
$cat 0;



        <
select name="cat" onChange="javascript:this.form.action='insert.php';  
        this.form.submit()"
>

        <
option value="" >Choose a category</option>
        <
option value="1" >Real-estate</option>
        <
option value="1" >Auto</option>

        </
select>


       
$field get_form_names($cat);
   if(
is_array($field))
   {
       
display_form($field);
   } 
As you see, I used javascript inside the select to refresh the page. Would this be similar in Codeigniter?