Refresh Software Documentation » Helios Calendar » Server Requirements

Helios Calendar is written in PHP, uses a MySQL database and will run on any OS that both PHP and MySQL are available for. Helios Calendar is developed and tested with Windows(IIS), Linux(Apache) and Mac(Apache) Operating Systems.

Important: The following information addresses many commonly asked questions related to hosting Helios Calendar, however, this document is not exhaustive. If you have a question that is not addressed by the information below, or if you have questions about a specific aspect of your unique hosting service/server, please contact us to discuss hosting Helios Calendar in further detail.


Minimum Versions



  • PHP (5.3.5+)
  • MySQL (5.5.x+)


  • PHP (5.5.x+)
  • MySQL (5.6.x+)

What's the Difference?

  • Required - Minimum for Helios Calendar to function.
  • Supported - Oldest version currently eligible for support.
  • Recommended - Recommended for the best experience.

Note: API integration for Facebook, Twitter & Google introduced in Helios Calendar 2.1 requires PHP 5.3 or newer.


PHP 4, 5.0 & 5.1

Helios Calendar will not work on these older versions of PHP and Refresh does not support them.

PHP 5.2

Support for this version of PHP has been discontinued.

PHP 5.3, 5.4 & 5.5

These versions are currently supported.


For complete functionality, support for the following libraries is required.

Additional Resources


Through version 2.0 Helios Calendar did not support MySQL running in ONLY_FULL_GROUP_BY mode. Users requiring support for this MySQL configuration should upgrade to version 2.0.1 (or newer).

MySQL 4.0, 4.1

Helios Calendar utilizes features not available on these older versions of MySQL and Refresh does not support them.

MySQL 5.0 & 5.1

Support for these version of MySQL has been discontinued. While there are currently no known performance issues on these platforms their use is not recommended.

MySQL 5.5 & 5.6

Both versions are currently supported.

Additional Resources

PHP & Hosting Settings/Requirements


  • fsockopen & Internet Connection - If fsockopen is disabled, or your server is not connected to the internet (or it's outgoing connection is restricted by a firewall), Helios will not install or upgrade successfully.
  • Directory Permissions - Helios Calendar requires the ability to write files to a limited number of directories for caching & image upload. Without the ability to write these files Helios Calendar will not function. Contact your web host support or system administrator to confirm PHP write privileges in your environment and to discuss the best practice for configuring PHP application write access on your server.
  • Facebook API Support - PHP 5.3+ with both CURL & OpenSSL libraries is required for Facebook API integration to work.


  • register_globals - Helios Calendar has no dependence on register_globals. It may remain in it's default "off" setting. (Note: This has been deprecated in PHP 5.3 and removed as of 5.4.)
  • short_open_tag - Helios Calendar offers full support for the default PHP5 setting of short_open_tag = off.

Sending Email

Helios Calendar supports authenticated & secure SMTP server connections. Email settings can be configured, and tested, within the admin console Preferences

Timezone Configuration

In some instances, dependent on PHP install configuration, users may see an error similar to:

date() []: It is not safe to rely on the system's timezone settings.

This error requires Helios Calendar users to:

  1. Identify their timezone. (List of PHP Timezones.)
  2. Add the following code to their config.php file.

Where Your_Timezone is the PHP supported timezone setting appropriate for your timezone.

Session Save Path Configuration

Some hosts require users to configure PHP applications to write session data to a temporary directory assigned to their hosting account. This process requires Helios Calendar users to:

  1. Identify their temporary directory path
  2. Add the following code into their config.php file.

To make this change add the following code to your Helios Calendar's /inc/config.php file.


Note: Insert the above code, updated for your unique server path, to your config.php file below line 11.


If you are unsure what your home directory path is please contact your hosting support or system administrator and they will be able to assist you further.

Confirmed Hosts That Require Session Save Path Configuration


Hosting Provider Specific Notes

Fasthosts Hosting Customers

It has been brought to Refresh's attention that under the Windows hosting service offered by Fasthosts they do not permit users to allow write access to directories for hosted apps. As a result Helios Calendar will not work with Fasthosts Windows hosting service.

Please reference this knowledge base article for more information.

GoDaddy Hosting Customers

Helios Calendar users have experienced anomalies with GoDaddy's PHP & MySQL configuration on their Windows Hosting Packages. GoDaddy hosting customers should use their Linux Hosting Package to host Helios, all reported issues related to GoDaddy hosting have been resolved by switching.

BizLand, FatCow, iPage, iPower and StartLogic Customers

Please see the note above about Session Save Path Configuration

Website Building Services

Helios Calendar is not compatible with hosted "build a website" services. Because these services only allow users to manipulate simple HTML content within a predefined framework and not upload custom files or site components (specifically: PHP applications) Helios Calendar will not work with these services.

It may be possible for you to utilize a subdomain to host Helios Calendar outside of these types of services, however, you should speak with your system administrator or service support to discuss this in detail and confirm what types of deployment your existing service(s) support, what configuration options are available and what additional services (if any) are required to achieve your unique deployment goals.

Incompatible Services

The following list is not exhaustive, if you are uncertain about the compatibility of your website or hosting please contact us with questions.

  • Blogger (and Google Sites)
  • Homestead (and Intuit branded variations: Intuit Websites, Intuit Website Builder, etc.)
  • Moonfruit
  • Ning
  • Squarespace
  • Viviti
  • Webs (Formerly Freewebs)
  • Weebly
  • Wix

Server Level Support

For your safety and ours, Refresh does not provide server level assistance as part of our software support services. If you have questions about any aspect of your server or hosting service (including, but not limited to: DNS or server configurations, installing or configuring PHP & MySQL, etc.) you should contact your web host support, system administrator or internal IT support staff.