How can I use PHP to dynamically publish an ical file to be read by Google Calendar?

Here's an example of how you can use the iCalcreator library to create an iCal file and output it for download:

<?php

require_once 'iCalcreator.class.php';

// Create a new iCal instance
$ical = new vcalendar();

// Set the calendar properties
$ical->setProperty( 'method', 'PUBLISH' );
$ical->setProperty( "x-wr-calname", "My Calendar" );
$ical->setProperty( "X-WR-CALDESC", "Events for my calendar" );
$ical->setProperty( "X-WR-TIMEZONE", "UTC" );

// Add an event
$event = & $ical->newComponent( 'vevent' );
$event->setProperty( 'dtstart', '20221215T090000', array( 'VALUE' => 'DATE-TIME' ));
$event->setProperty( 'dtend', '20221215T170000', array( 'VALUE' => 'DATE-TIME' ));
$event->setProperty( 'summary', 'Christmas Day' );
$event->setProperty( 'description', 'Celebrate Christmas with family and friends' );
$event->setProperty( 'location', 'My House' );

// Output the iCal file for download
header( 'Content-Type: text/calendar; charset=utf-8' );
header( 'Content-Disposition: attachment; filename="calendar.ics"' );
echo $ical->returnCalendar();

?>

This script creates a new instance of the vcalendar class, sets some calendar properties, and adds an event to the calendar. Then it sets the appropriate headers to make the iCal file downloadable and outputs the file using the $ical->returnCalendar() method. Now you can provide a link to this script file on your website and your users can import the events into their Google Calendar by clicking on the link.