Moodle : I Am Stuck in Getting Context id when i tried to insert image in database

Question

require_once("$CFG->libdir/formslib.php");

class block_add_edit_form extends moodleform {
    public function definition()
    {
        global $CFG,$DB;
        $mform = $this->_form;

        $mform->addElement('text', 'id');
        $mform->setType('id', PARAM_INT);

        $mform->addElement('editor', 'attachment',get_string('file', 'block_add'),);
        $mform->setType('attachment', PARAM_RAW);
        $this->add_action_buttons();



    }
    function validation($data, $files) {
        return array();
    }

This is my form where i assigning values, down below is the code where i want insert but getting this error

Coding error detected, it must be fixed by a programmer: Invalid context id specified context::instance_by_id() Debug info: Error code: codingerror Stack trace:

line 5346 of \lib\accesslib.php: coding_exception thrown line 1776 of \lib\blocklib.php: call to context::instance_by_id() line 1478 of \lib\blocklib.php: call to block_manager->process_url_edit() line 1645 of \lib\pagelib.php: call to block_manager->process_url_actions() line 1110 of \lib\pagelib.php: call to moodle_page->starting_output() line 1391 of \lib\outputrenderers.php: call to moodle_page->set_state() line 179 of \my\index.php: call to core_renderer->header()

require_once (__DIR__ . '/../../config.php');
require_once('edit_form.php');

$mform = new block_add_edit_form();

global $DB;

if ($mform->is_cancelled()) {
    print_r("1");
}else if ($fromform = $mform->get_data()) {
    var_dump($mform->get_data());
    $record = new stdClass();
    $record->id = $fromform->id;
    $record->attachment = $fromform->attachment;
    $DB->insert_record('image', $record);
 }

 echo $OUTPUT->header();
 $mform->display();

 echo $OUTPUT->footer();