This script allows you to output a MySQL table content as an iCalendar file.

iCalendar.php

<?php
// This work by Marcel Patzsch is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License.
// To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/4.0/.
// Based on a work at https://gist.github.com/jakebellacera/635416.

// Notes:
//  - Variables labeled with (!) are required. Non required variables can be set to "" or delete.
//
//  - iCal requires a date format of "yyyymmddThhiissZ". The "T" and "Z"
//    characters are not placeholders, just plain ol' characters. The "T"
//    character acts as a delimeter between the date (yyyymmdd) and the time
//    (hhiiss), and the "Z" states that the date is in UTC time. Note that if
//    you don't want to use UTC time, you must set a timzone.
//
//  - Read up on RFC 5545, the iCalendar specification. There is a lot of helpful
//    info in there, such as formatting rules. There are also many more options
//    to set, including alarms, invitees, busy status, etc.
//
//    http://tools.ietf.org/html/rfc5545

$Filename = "Calendar.ics";			//Filename (!)
$Calname = "Calendarname";			//Calendarname
$Timezone = "America/New_York";			//Timezone

$dbServer = "localhost";			//Database Address (!)
$dbUser = "dbuser";				//Database User (!)
$dbPass = "dbpass";				//Database Password (!)
$dbName = "dbname";				//Database Name (!)
$dbSelect = "Select * FROM Tablename"; 		//Database Select (!)

$dbTitleColumn = "Title";			//Table column name: Name of the Event (!)
$dbPriorityColumn = "Priority";			//Table column name: Priority of the Event
$dbLocationColumn = "Location";			//Table column name: Location/Address of the Event
$dbCreationDateColumn = "Created";		//Table column name: Creation Date of the Event
$dbStartDateColumn = "Start";			//Table column name: Start Date of the Event (!)
$dbEndDateColumn = "End";			//Table column name: End Date of the Event (!)
$dbDescriptionColumn = "Decription";		//Table column name: Description of the Event
$dbCommentColumn = "Comment";			//Table column name: Comment of the Event

header("Pragma: public"); 
header("Expires: 0"); 
header("Cache-Control: must-revalidate, post-check=0, pre-check=0"); 
header("Cache-Control: private",false); 
header("Content-Type: application/force-download"); 
header("Content-Type: application/octet-stream"); 
header("Content-Type: application/download");
header("Content-Type: text/Calendar");
header("Content-Disposition: attachment; filename=\"".$Filename."\";"); 
header("Content-Description: File Transfer"); 
header("Content-Transfer-Encoding: binary"); 

echo "BEGIN:VCALENDAR\r\n";			//BEGIN CAL
echo "VERSION:2.0\r\n";				//VERSION: RFC 5545 section 3.7.4
if (isset($Calname) && $Calname != "")
	echo "X-WR-CALNAME:".$Calname."\r\n";	//NO RFC 5545 STANDARD
echo "PRODID:PHP\r\n";				//PRODUCT IDENTIFIER: RFC 5545 section 3.7.3
echo "CALSCALE:GREGORIAN\r\n";			//CALSCALE: RFC 5545 section 3.7.1
echo "METHOD:PUBLISH\r\n";			//METHOD: RFC 5545 section 3.7.2

if (!mysql_connect($dbServer, $dbUser, $dbPass))
    die ("Connection to DB-Server failed.");
if (!mysql_select_db($dbName))
    die ("Database not found.");
mysql_query("SET CHARACTER SET 'utf8'");

$query = mysql_query($dbSelect);   
while($Column = mysql_fetch_array($query)){
	echo "BEGIN:VEVENT\r\n";								//BEGIN EVENT
	
	echo "SUMMARY:".addslashes($Column[$dbTitleColumn])."\r\n";				//SUMMARY: RFC 5545 section 3.8.1.12
	
	if (isset($dbPriorityColumn) && $dbPriorityColumn != "")
		echo "PRIORITY:".addslashes($Column[$dbPriorityColumn])."\r\n";			//PRIORITY: RFC 5545 section 3.8.1.9
		
	if (isset($dbLocationColumn) && $dbLocationColumn != "")
		echo "LOCATION:".addslashes($Column[$dbLocationColumn])."\r\n";			//LOCATION: RFC5545 section 3.8.1.7	
		
	if (isset($dbCreationDateColumn) && $dbCreationDateColumn != "") {			//DATE-TIME STAMP: RFC 5545 section 3.8.7.2
		if (isset($Timezone) && $Timezone != "")
			echo "DTSTAMP;TZID=".$Timezone.":".formateDate(strtotime($Column[$dbCreationDateColumn]),$Timezone)."\r\n";	
		else
			echo "DTSTAMP:".formateDate(strtotime($Column[$dbCreationDateColumn]),$Timezone)."\r\n";	
	}
	
	if (isset($Timezone) && $Timezone != "")						//DATE-TIME START: RFC 5545 section 3.8.2.4
		echo "DTSTART;TZID=".$Timezone.":".formateDate(strtotime($Column[$dbStartDateColumn]),$Timezone)."\r\n";	
	else
		echo "DTSTART:".formateDate(strtotime($Column[$dbStartDateColumn]),$Timezone)."\r\n";	
		
	if (isset($Timezone) && $Timezone != "")						//DATE-TIME END: RFC 5545 section 3.8.2.2
		echo "DTEND;TZID=".$Timezone.":".formateDate(strtotime($Column[$dbEndDateColumn]),$Timezone)."\r\n";	
	else
		echo "DTEND:".formateDate(strtotime($Column[$dbEndDateColumn]),$Timezone)."\r\n";	
	
	if (isset($dbDescriptionColumn) && $dbDescriptionColumn != "")
		echo "DESCRIPTION:".addslashes($Column[$dbDescriptionColumn]). "\r\n";		//DESCRIPTION: RFC 5545 section 3.8.1.5
		
	if (isset($dbCommentColumn) && $dbCommentColumn != "")
		echo "COMMENT:".addslashes($Column[$dbCommentColumn]). "\r\n";			//COMMENT: RFC 5545 section 3.8.1.4
		
	echo "END:VEVENT\r\n";									//END EVENT
}

echo "END:VCALENDAR";				//END CAL


//-----------------------------------------------------------------------------------------------------------------//


// Converts a unix timestamp to an ics-friendly format
// NOTE: "Z" means that this timestamp is a UTC timestamp. If $Timezone
// is set, the timestamp is interpreted as a local timestamp and DTEND, DTSTAMP and DTSTART
// are modifyed with TZID properties. Else the timestamp is interpreted as a UTC timestamp.
//
// Also note that we are using "H" instead of "g" because iCalendar's Time format
// requires 24-hour time (see RFC 5545 section 3.3.12 for info).
function formateDate($time,$timezone) {
	if (isset($timezone) && $timezone != "")
		return date('Ymd\THis', $time);
	else
		return date('Ymd\THis\Z', $time);
}
?>