Q:

Insert comment linked to post ID

Trying to Insert into report_comment table ReportID and Comments into Repot_comments table
However I now get errors
 Error Number: 1064

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '0) VALUES ('Report_Comments')' at line 1

INSERT INTO `Report_Comments` (0) VALUES ('Report_Comments')

Filename: models/report/Report_model.php

Line Number: 61

Controller 
 function comment_add()
        {
                if ($query = $this->report_model->create_comment()) {

                    $this->session->set_flashdata('messagetwo', 'You added a Comment');
                    redirect('main/comments/' .$_POST['ReportID']);

                } else {
                    $this->session->set_flashdata('messagetwo', 'Sorry not this time');
                    redirect('main/comments/' .$_POST['ReportID']);
                }
        }

Model 
function create_comment()
{

    $new_comment = array(
        'Comments', $_POST => $this->input->post('Report_Comments')
    );

    $insert = $this->db->insert('Report_Comments', $new_comment);
    return $insert;
}

View
    <p><?= anchor('main', 'Back home'); ?></p>

    <?= form_open('main/comment_add'); ?>

    <?= form_hidden('ReportID', $this->uri->segment(3)); ?>

    <p><textarea name="Comments" rows="10"></textarea></p>
    <p><input type="submit" value="add comment"/></p>

    <?php
    if ($this->session->flashdata('messagetwo')) {
        ?>
        <div class="message flash">
            <?php echo $this->session->flashdata('messagetwo'); ?>
        </div>
        <?php
    }
    ?>

    </form>

A:

The problem is your:
$new_comment = array(
        'Comments', $_POST => $this->input->post('Report_Comments')
    );

Check with a var_dump($new_comment), the first index should be 0;
Try that:
$new_comment = array(
        'Comments' => $this->input->post('Report_Comments')
    );

Assuming your field is "Comments" and $this->input->post('Report_Comments') return a valid string.
Here is the documentation of $this->db->insert() for codeigniter

