发布请求不会更改DB中的值

I can't seem to figure out why my status doesn't change. I am trying to get my chat activation button to work on click, and send a post request to a specified url via jQuery. Can I even do that without using an actual form or sth??

jQuery:

$(".model_chat_button").css('cursor', 'pointer').click(function() {
            var model_id = $(this).parent().attr('id').split('model_')[1];


            var active = 1;
            if ($(this).attr('rel') == '1')
            {
                active = 0;
                $(this).attr('rel', '0');
                $(this).find("img").attr('src', $(this).find("img").attr('src').replace('chat_active', 'chat_inactive'));
            }
            else
            {
                $(this).attr('rel', '1');
                $(this).find("img").attr('src', $(this).find("img").attr('src').replace('chat_inactive', 'chat_active'));
            }


            $.post(base_url + lang + '/chats/activateModel',{model_id: model_id, active: active});


        });

In my controller chats.php:

 public function activateModel()
{
    if ($this->session->userdata('is_admin') && $this->input->post('model_id'))
    {
        $model = new Model($this->input->post('model_id'));
        $model->chat_active = $this->input->post('active')? 1 : 0;
        $model->save();
    }
}

And my view:

<div id="<?php echo $model->id; ?>"> 

    <div class="model_chat_button" rel="<?php echo $model->chat_active? 1 : 0;?>">
    <?php if ($model->chat_active): ?>
    <?php if (! $this->session->userdata('is_admin')): ?>
    <a href="<?php echo site_url(); ?>/chat/<?php echo $model->id; ?>" title="<?php echo $this->lang->line('chat_with'); ?> <?php echo $model->name; ?>">
    <?php endif; ?>
    <img src="<?php echo base_url(); ?>assets/images/design/button_chat_active.png" alt="Chat" />
    <?php if (! $this->session->userdata('is_admin')): ?>
    </a>
    <?php endif; ?>
    <?php else: ?>
    <img src="<?php echo base_url(); ?>assets/images/design/button_chat_inactive.png" alt="Chat" />
    <?php endif; ?>



    </div>
    </div>

So from what I can tell from the network tab, it does send a post request to the chats/activateModel URL, but the model ID is not added. What am I missing here?