codeigniter and ajax autosave doesn't work

Question

I have a timer let's say 60 minutes and I want to save the timer every 1 second interval. My code is working perfectly locally but when I uploaded online. It doesn't work anymore. I got "500 (Internal Server Error)" Please help me. Your help are very much appreciated. Thank you so much guys!

Database

CREATE TABLE IF NOT EXISTS `timer` (
  `id` int(6) NOT NULL,
  `time` int(6) NOT NULL COMMENT 'in minutes',
  `remaining_time` int(6) NOT NULL COMMENT 'seconds',
  `type_id_fk` int(6) NOT NULL,
  `section` int(6) NOT NULL,
  `user_id_fk` int(6) NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

Controller

public function updatetimer() {
        $this->Mpractice->updateTimer();
    }

Model

function updateTimer() {
        //TIMER VAR
        $timer_id = $this->input->post('timer_id');
        $remaining_time = $this->input->post('remainingTime');

        $this->db->trans_start();
        $this->db->query("UPDATE `toefl`.`timer` SET `remaining_time` = '$remaining_time' WHERE `timer`.`id` = $timer_id;");
        $this->db->trans_complete();
}

View

<div class="clock"></div>
<form method="post" action="">
    <input type="hidden" id="remainingTime" value="<?= $this->Mpractice->get_timer($type); ?>">
    <input type="hidden" id="timer_id" name="timer_id" value="<?= $this->Mpractice->get_timer_id($type); ?>">
</form>

Script

<script>
    $(document).ready(function () {
//        GET REMAINING TIME
        var doUpdate = function () {
            $('#remainingTime').each(function () {
                var count = parseInt($(this).val());
                if (count !== 0) {
                    $(this).val(count - 1);
                }
            });
        };
        // Schedule the update to happen once every second
        setInterval(doUpdate, 1000);
//        UPDATE TIMER EVERY 1SECOND
        setInterval(function () {
        $("#remainingTime, #timer_id").autosave({
            url: "<?= site_url('practice/updatetimer'); ?>",
            type: "POST",
            dataType: "html",
            grouped: true, //send data for all fields with the autosave
            success: function () {
            }
        });
        }, 1000);
    });
</script>

Answer 1

Solution 1: check it first , You have use ** short tag [ <?= ?>] **in your form please check in phpinfo short tag is on or off in your live server.

Solution 2: If you get 500 internal sever error in code you have most probably Syntax problem or SQL query problem. please check it.

If you working with AJAX please check console to get all PHP ERORR in response.