A convenient script to generate iCalendar (.ics) files on the fly in PHP.

_PHPtoICS.md

PHP to ICS

This gist contains a convenient script to generate iCalendar (.ics) files on the fly in PHP.

Basic usage

include 'ICS.php'

$properties = array(
  'dtstart' => 'now',
  'dtend' => 'now + 30 minutes'
);

$ics = new ICS($properties);
$ics_file_contents = $ics->to_string();

Available properties

• description - string description of the event.
• dtend - date/time stamp designating the end of the event. You can use either a DateTime object or a PHP datetime format string (e.g. "now + 1 hour").
• dtstart - date/time stamp designating the start of the event. You can use either a DateTime object or a PHP datetime format string (e.g. "now + 1 hour").
• location - string address or description of the location of the event.
• summary - string short summary of the event - usually used as the title.
• url - string url to attach to the the event. Make sure to add the protocol (http:// or https://).

Detailed examples

Button that downloads an ICS file when clicked

This example contains a form on the front-end that submits to a PHP script that initiates a download of an ICS file. This example uses hidden form fields to set the properties dynamically.

index.html

<form method="post" action="/download-ics.php">
  <input type="hidden" name="date_start" value="2017-1-16 9:00AM">
  <input type="hidden" name="date_end" value="2017-1-16 10:00AM">
  <input type="hidden" name="location" value="123 Fake St, New York, NY">
  <input type="hidden" name="description" value="This is my description">
  <input type="hidden" name="summary" value="This is my summary">
  <input type="hidden" name="url" value="http://example.com">
  <input type="submit" value="Add to Calendar">
</form>

download-ics.php

<?php

include 'ICS.php';

header('Content-Type: text/calendar; charset=utf-8');
header('Content-Disposition: attachment; filename=invite.ics');

$ics = new ICS(array(
  'location' => $_POST['location'],
  'description' => $_POST['description'],
  'dtstart' => $_POST['date_start'],
  'dtend' => $_POST['date_end'],
  'summary' => $_POST['summary'],
  'url' => $_POST['url']
));

echo $ics->to_string();

ICS.php

<?php

/**
 * This is free and unencumbered software released into the public domain.
 * 
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 * 
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 * 
 * For more information, please refer to <http://unlicense.org>
 * 
 * ICS.php
 * =============================================================================
 * Use this class to create an .ics file.
 * 
 *
 * Usage
 * -----------------------------------------------------------------------------
 * Basic usage - generate ics file contents (see below for available properties):
 *   $ics = new ICS($props);
 *   $ics_file_contents = $ics->to_string();
 *
 * Setting properties after instantiation
 *   $ics = new ICS();
 *   $ics->set('summary', 'My awesome event');
 *
 * You can also set multiple properties at the same time by using an array:
 *   $ics->set(array(
 *     'dtstart' => 'now + 30 minutes',
 *     'dtend' => 'now + 1 hour'
 *   ));
 *
 * Available properties
 * -----------------------------------------------------------------------------
 * description
 *   String description of the event.
 * dtend
 *   A date/time stamp designating the end of the event. You can use either a
 *   DateTime object or a PHP datetime format string (e.g. "now + 1 hour").
 * dtstart
 *   A date/time stamp designating the start of the event. You can use either a
 *   DateTime object or a PHP datetime format string (e.g. "now + 1 hour").
 * location
 *   String address or description of the location of the event.
 * summary
 *   String short summary of the event - usually used as the title.
 * url
 *   A url to attach to the the event. Make sure to add the protocol (http://
 *   or https://).
 */

class ICS {
  const DT_FORMAT = 'Ymd\THis\Z';

  protected $properties = array();
  private $available_properties = array(
    'description',
    'dtend',
    'dtstart',
    'location',
    'summary',
    'url'
  );

  public function __construct($props) {
    $this->set($props);
  }

  public function set($key, $val = false) {
    if (is_array($key)) {
      foreach ($key as $k => $v) {
        $this->set($k, $v);
      }
    } else {
      if (in_array($key, $this->available_properties)) {
        $this->properties[$key] = $this->sanitize_val($val, $key);
      }
    }
  }

  public function to_string() {
    $rows = $this->build_props();
    return implode("\r\n", $rows);
  }

  private function build_props() {
    // Build ICS properties - add header
    $ics_props = array(
      'BEGIN:VCALENDAR',
      'VERSION:2.0',
      'PRODID:-//hacksw/handcal//NONSGML v1.0//EN',
      'CALSCALE:GREGORIAN',
      'BEGIN:VEVENT'
    );

    // Build ICS properties - add header
    $props = array();
    foreach($this->properties as $k => $v) {
      $props[strtoupper($k . ($k === 'url' ? ';VALUE=URI' : ''))] = $v;
    }

    // Set some default values
    $props['DTSTAMP'] = $this->format_timestamp('now');
    $props['UID'] = uniqid();

    // Append properties
    foreach ($props as $k => $v) {
      $ics_props[] = "$k:$v";
    }

    // Build ICS properties - add footer
    $ics_props[] = 'END:VEVENT';
    $ics_props[] = 'END:VCALENDAR';

    return $ics_props;
  }

  private function sanitize_val($val, $key = false) {
    switch($key) {
      case 'dtend':
      case 'dtstamp':
      case 'dtstart':
        $val = $this->format_timestamp($val);
        break;
      default:
          $val = $this->escape_string($val);
          $val = str_replace("\r\n", "\\n", $val);
          $val = $this->ical_split($val);
    }

    return $val;
  }

  private function format_timestamp($timestamp) {
    $dt = new DateTime($timestamp);
    return $dt->format(self::DT_FORMAT);
  }

  private function escape_string($str) {
    return preg_replace('/([\,;])/','\\\$1', $str);
  }
  
  function ical_split($value) {
      /* "fold" any long content lines  See: http://www.ietf.org/rfc/rfc2445.txt, section 4.1
       * Copied from answer of anmari at stackoverflow on topic https://stackoverflow.com/questions/48696534/ics-content-line-validation-and-html-in-description
       * */
      
      $value = trim($value);
      $lines = array();
      while (strlen($value)>(75)) {
          $line = mb_substr($value, 0, 75);
          $llength = mb_strlen($line);  //  must use mb_strlen with mb_substr otherwise will not work things like &nbsp;
          $lines[] = $line.chr(13).chr(10).chr(32); /* CRLF and space*/
          $value = mb_substr($value, $llength); /* set value to what's left of the string */
      }
      
      if (!empty($value)) {
          $lines[] = $value; /* the last line does not need a white space */
      }
      return (implode($lines));
  }
}

you split the line at 75 chars chunks and add after that the space. This will result in line length of 76 and result in an error if there are more than 2 lines after the split