Veri tabanına (Sıfır Eklenmiyor)

<?php
include("../config.php");

if (isset($_POST['id'])) {

    //collect data
    $error      = null;
    $id         = $_POST['id'];
    $start      = $_POST['start'];
    $end        = $_POST['end'];
  $borclu      = $_POST['total'] - $_POST['kapora'];
    //optional fields
    $title      = isset($_POST['title']) ? $_POST['title']: '';
    $tc_no      = isset($_POST['tc_no']) ? $_POST['tc_no']: '';
    $telefon    = isset($_POST['telefon']) ? $_POST['telefon']: '';
    $total      = isset($_POST['total']) ? $_POST['total']: '';
    $kapora     = isset($_POST['kapora']) ? $_POST['kapora']: '';
    $color      = isset($_POST['color']) ? $_POST['color']: '';
    $text_color = isset($_POST['text_color']) ? $_POST['text_color']: '';
   

    //validation
    if ($start == '') {
        $error['start'] = 'Start date is required';
    }

    if ($end == '') {
        $error['end'] = 'End date is required';
    }

    //if there are no errors, carry on
    if (! isset($error)) {

        //reformat date
        $start = date('Y-m-d H:i:s', strtotime($start));
        $end = date('Y-m-d H:i:s', strtotime($end));
        
        $data['success'] = true;
        $data['message'] = 'Success!';

        //set core update array
        $update = [
            'start_event' => date('Y-m-d H:i:s', strtotime($_POST['start'])),
            'end_event' => date('Y-m-d H:i:s', strtotime($_POST['end']))
        ];

        //check for additional fields, and add to $update array if they exist
        
        if ($tc_no !='') {
            $update['tc_no'] = $tc_no;
        }

        if ($title !='') {
            $update['title'] = $title;
        }

        if ($total !='') {
            $update['total'] = $total;
        }

       if ($borclu !='') {
            $update['borclu'] = $borclu;
        }

        if ($kapora !='') {
            $update['kapora'] = $kapora;
        }

        if ($telefon !='') {
            $update['telefon'] = $telefon;
        }


        if ($color !='') {
            $update['color'] = $color;
        }

        if ($text_color !='') {
            $update['text_color'] = $text_color;
        }

        //set the where condition ie where id = 2
        $where = ['id' => $_POST['id']];

        //update database
        $db->update('events', $update, $where);
      
    } else {

        $data['success'] = false;
        $data['errors'] = $error;
    }

    echo json_encode($data);
}

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