为什么会出现500 Internal Server Error？

Question

I'm learning so far, but this db ajax communication always makes me bang my head against the wall.

This is the controller:

function become_teacher()
{   
    $this->load->model('class_model');
    $data = array('user_id' => $this->input->post('user_id'),
        'group_id' => $this->input->post('user_group') 
    );
    $this->class_model->change_to_teacher($data);
}

Here is the Model:

function change_to_teacher($data)
{
    $this->db->insert('user_groups', $data);
    return;     
}

And here is the script:

<p>Om du vill kunna skapa lektionen bli lärare. </p>
<button class="btn teacher">Bli lärare</button>

<script type="text/javascript">
    var user_id = $('.meta').text().trim();
    var user_group = '4';
    $('.teacher').on('click', function() {
        $.ajax({
            type: "POST",
            url: "http://localhost:8888/testing/index.php/cours/become_teacher",
            data: "{ user_id: user_id, user_group: user_group }",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
        });
    });
</script>

The var user_id is getting its data from the header file, not included here. Any help would be much appreciated!

Answer 1

Don't know the detail, but

data: "{ user_id: user_id, user_group: user_group}",

Should be

data: { "user_id": user_id, "user_group": user_group},

Answer 2

I've missed a letter when defining the table. Now its working...