<?php
$from_name = "Your Name";
$from_address = "youremail@yourdomain.com";
$to_name = "Receiver Name"
$to_address = "receiveremail@yourdomain.com";
$startTime = "04/15/2020 12:00:00";
$endTime = "04/15/2020 12:30:00";
$subject = "Reminder for event";
$description = "eminder for event";
$location = "Your Location";
$domain = 'yourdomain.com';
$mime_boundary = "----Meeting Booking----".MD5(TIME());
$headers = "From: ".$from_name." <".$from_address.">\n";
$headers .= "Reply-To: ".$from_name." <".$from_address.">\n";
$headers .= "MIME-Version: 1.0\n";
$headers .= "Content-Type: multipart/alternative; boundary=\"$mime_boundary\"\n";
$headers .= "Content-class: urn:content-classes:calendarmessage\n";
$message = "--$mime_boundary\r\n";
$message .= "Content-Type: text/html; charset=UTF-8\n";
$message .= "Content-Transfer-Encoding: 8bit\n\n";
$message .= "<html>\n";
$message .= "<body>\n";
$message .= 'Demo Message';
$message .= "</body>\n";
$message .= "</html>\n";
$message .= "--$mime_boundary\r\n";
$ical = 'BEGIN:VCALENDAR' . "\r\n" .
'PRODID:-//Microsoft Corporation//Outlook 10.0 MIMEDIR//EN' . "\r\n" .
'VERSION:2.0' . "\r\n" .
'METHOD:REQUEST' . "\r\n" .
'BEGIN:VTIMEZONE' . "\r\n" .
'TZID:Eastern Time' . "\r\n" .
'BEGIN:STANDARD' . "\r\n" .
'DTSTART:20091101T020000' . "\r\n" .
'RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=1SU;BYMONTH=11' . "\r\n" .
'TZOFFSETFROM:-0400' . "\r\n" .
'TZOFFSETTO:-0500' . "\r\n" .
'TZNAME:EST' . "\r\n" .
'END:STANDARD' . "\r\n" .
'BEGIN:DAYLIGHT' . "\r\n" .
'DTSTART:20090301T020000' . "\r\n" .
'RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=2SU;BYMONTH=3' . "\r\n" .
'TZOFFSETFROM:-0500' . "\r\n" .
'TZOFFSETTO:-0400' . "\r\n" .
'TZNAME:EDST' . "\r\n" .
'END:DAYLIGHT' . "\r\n" .
'END:VTIMEZONE' . "\r\n" .
'BEGIN:VEVENT' . "\r\n" .
'ORGANIZER;CN="'.$from_name.'":MAILTO:'.$from_address. "\r\n" .
'ATTENDEE;CN="'.$to_name.'";ROLE=REQ-PARTICIPANT;RSVP=TRUE:MAILTO:'.$to_address. "\r\n" .
'LAST-MODIFIED:' . date("Ymd\TGis") . "\r\n" .
'UID:'.date("Ymd\TGis", strtotime($startTime)).rand()."@".$domain."\r\n" .
'DTSTAMP:'.date("Ymd\TGis"). "\r\n" .
'DTSTART;TZID="Pacific Daylight":'.date("Ymd\THis", strtotime($startTime)). "\r\n" .
'DTEND;TZID="Pacific Daylight":'.date("Ymd\THis", strtotime($endTime)). "\r\n" .
'TRANSP:OPAQUE'. "\r\n" .
'SEQUENCE:1'. "\r\n" .
'SUMMARY:' . $subject . "\r\n" .
'LOCATION:' . $location . "\r\n" .
'CLASS:PUBLIC'. "\r\n" .
'PRIORITY:5'. "\r\n" .
'BEGIN:VALARM' . "\r\n" .
'TRIGGER:-PT15M' . "\r\n" .
'ACTION:DISPLAY' . "\r\n" .
'DESCRIPTION:Reminder' . "\r\n" .
'END:VALARM' . "\r\n" .
'END:VEVENT'. "\r\n" .
'END:VCALENDAR'. "\r\n";
$message .= 'Content-Type: text/calendar;name="meeting.ics";method=REQUEST'."\n";
$message .= "Content-Transfer-Encoding: 8bit\n\n";
$message .= $ical;
mail($to_address, $subject, $message, $headers);
?>