event.php

<?php
require_once __DIR__ . '/vendor/autoload.php';

require_once('connect_db.php');

session_start();

define('CLIENT_SECRET_PATH', __DIR__ . '/client_secret.json');
define('SCOPES', implode(' ', array(
  Google_Service_Calendar::CALENDAR)
));

if(!isset($_SESSION['faculty']))
  $_SESSION['faculty'] = $_SESSION['uName'];
 // echo $_SESSION['faculty'];
function getClient() {
  $client = new Google_Client();
  $client->setScopes(SCOPES);
  $client->setAuthConfigFile(CLIENT_SECRET_PATH);
  $client->setAccessType('offline');

  if (isset($_SESSION['access_token']) && $_SESSION['access_token']) {
    $client->setAccessToken($_SESSION['access_token']);
  }
  // Refresh the token if it's expired.
  if ($client->isAccessTokenExpired()) {
    $client->refreshToken($client->getRefreshToken());
  }
  return $client;
}

function updateDB($id_list) {
    global $db;
  $query_string = "SELECT COUNT(*) AS count FROM events where fac_id = ?";
  $query = $db->prepare($query_string);
  $query->execute([$_SESSION['faculty']]);
  while($count = $query->fetch()){
      if($count['count']==='0'){
        $query_string = "INSERT INTO events VALUES(?,?)";
        $query = $db->prepare($query_string);
        $query->execute([$_SESSION['faculty'],$id_list]);
      }
      else{
        $query_string = "update events set eventID=? where fac_id=?";
        $query = $db->prepare($query_string);
        $query->execute([$id_list,$_SESSION['faculty']]);
      }
  }
  header('Location: /');
}

function add_events($event_array, $service) {
  foreach ($event_array as &$values){
    $event = new Google_Service_Calendar_Event($values);
    $event = $service->events->insert('primary', $event);
    $id_list .= ',' . $event->getId();
  }
  // $id_list = mysql_real_escape_string($id_list);
  //updating the events table with the latest event IDs added to the google calender
  updateDB($id_list);
  printf("added events \n");
}

function delete_events($fac_id, $service) {
    global $db;

  $query_string = "select * from events where fac_id=?";
  $query = $db->prepare($query_string);
  $query->execute([$_SESSION['faculty']]);

  while($id_list = $query->fetch()){
      $id_arr = explode(',', $id_list['event_id']);
      foreach ($id_arr as &$values)
          if ($values!='') {
            try {
              $service->events->delete('primary', $values);
            } catch (Exception $e) {}
          }
    }
}

$client = getClient();
$service = new Google_Service_Calendar($client);

delete_events($_SESSION['faculty'], $service);

$query_string="select A.course_id, course_name, day, slot_num, room, table_name  from courses as A join slot_allocs as B where A.course_id=B.course_id and A.fac_id=?";
$query = $db->prepare($query_string);
$query->execute([$_SESSION['faculty']]);
$retval = $query->fetch();


// semester starting date
$semStartDate = 1;
$semEndDate = 30;
$semStartMonth = intval(date('m'));
if($semStartMonth<=4){
  $semStartMonth = 1;
  $semEndMonth = 4;
}
else{
  $semStartMonth = 8;
  $semEndMonth = 11;
}
$year = date('Y');


// monday ==> 1, sunday==>0
$semStartDay = date('w', strtotime("".$year."-".$semStartMonth."-".$semStartDate));

$slot_mapping = array(
        '09:00:00-09:55:00',
        '10:00:00-10:55:00',
        '11:00:00-11:55:00',
        '12:00:00-12:55:00',
        '13:00:00-14:25:00',
        '14:30:00-15:55:00',
        '16:00:00-17:25:00',
        '17:30:00-19:00:00',
        '19:00:00-20:30:00',
);

$event_array = array();

while($row = $query->fetch())
{
  $dayOffset = $row['day']-$semStartDay;
  if ($dayOffset<0)
    $dayOffset += 7;

  $firstclassDate = $semStartDate + ($dayOffset)%7;

  $eventDate = date_format(date_create($year."-".$semStartMonth."-".$firstclassDate, timezone_open('Asia/Kolkata')), 'Y-m-d');

  // get event's start and end time
  $timestring = explode('-', $slot_mapping[$row['slot_num']-1]);
  $eventStarttime = $timestring[0];
  $eventEndtime = $timestring[1];

  $untilDate = date_format(date_create($year."-".$semEndMonth."-".$semEndDate, timezone_open('Asia/Kolkata')), 'Ymd');

  $event=array(
  'summary' => $row['course_id'] . " : " . $row['course_name'],
  'location' => $row['room'],

  'start' => array(
    'dateTime' => $eventDate."T".$eventStarttime."+05:30",
    'timeZone' => 'Asia/Kolkata',
  ),
  'end' => array(
    'dateTime' => $eventDate."T".$eventEndtime."+05:30",
    'timeZone' => 'Asia/Kolkata',
  ),
    'recurrence' => array(
    'RRULE:FREQ=WEEKLY;UNTIL='.$untilDate.'T235959Z'
  ),

  'reminders' => array(
    'useDefault' => FALSE,
    'overrides' => array(
      array('method' => 'email', 'minutes' => 24 * 60),
      array('method' => 'popup', 'minutes' => 10),
    ),
  ),

 );
  // push the above event now to array
  array_push($event_array,$event);
}

//add events to calendar
add_events($event_array, $service);
header('Location: /');
?>