Code Igniter php - return (ajax?) data based on dropdown selection with JQuery

I want to generate some data for editing, filtered by the choice a user makes in a dropdown menu, but I don't want to complicate things.

I already have my project querying the database for a list of "trees", and populating a dropbox with the tree name, assigning the tree_id as its value.

All I want to do is, when the user makes a choice in the drop-down, have JQuery return a list of only that ID's relevant data (description, etc).

What's the simplest way to do that? Do I even need to make an AJAX request? Here's my code:

CONTROLLER:

$this->load->model('Model_form','', TRUE);
$data['trees'] = $this->Model_form->get_tree();
$this->load->view('view_form_tree', $data);

MODEL:

function get_tree(){
$query = $this->db->query('SELECT * FROM trees'开发者_StackOverflow);
return $query->result();
}

VIEW:

<h1>Edit Tree</h1>
<select id="f_treeindex" name="f_treeindex" class="dd_black">
<option value=""></option>
<?php
foreach($trees as $tree){
    echo '<option value="' . $tree->id . '">' . $tree->tree_name . '</option>';
}
?>
</select>

<script type="text/javascript">
     $(document).ready(function() {
        $('#f_treeindex').change(function(){
            var tree_id = $('#f_treeindex').val();
            if (tree_id != ""){
                //DO WHATEVER I NEED TO DO TO CALL THE INFORMATION FOR THE TREE WHOSE ID MATCHES THAT SELECTED IN THE DROPDOWN
            }//end if
        }); //end change
     }); //end docready
</script>

Just a note that the SELECT * statement in the model will return the tree_id, tree_name, and tree_description.

If you make a 'show' controller method that returns a bare template with the data (ie: not with the full layout), you can do something like this:

$('#f_treeindex').change(function(){
    var tree_id = $('#f_treeindex').val();
    if (tree_id != ""){
        $.get('/controller_name/show', {id:tree_id}, function(data){
            $(this).parents('div').append(data);
        })
    }//end if
});

Wrap the <select> in a <div> so your jquery has something to append the resulting html to.

Also, I would rename get_tree() to get_trees(), that way you can also do a get_tree($id) that returns a single tree in your controller_name#show method, which you can have return a template without the layout, to be appended.

function show() {
    $this->load->model('Model_form','', TRUE);
    $data['tree'] = $this->Model_form->get_tree($this->params['id']);
    $this->load->view('single_tree_view', $data);
}

also, not 100% sure how your CI is set up, so your $.get line might need to be

$.get('/controller_name/show/'+tree_id, function(data){...