This article explains the differences between versions of PHP, which ones are available to you and how to select a version to use.

Supported Versions

The supported versions of PHP vary depending on your control panel and operating system.  This table was last revised 03/14/2014.

PHP versions prior to 5.3, except 5.1.6 on CentOS 5, are unsupported and considered End of Life.  This includes all versions of PHP 4.x.  CentOS 5's PHP 5.1.6 receives bug and security fixes through the CentOS project, and will remain supported as long as CentOS 5 is supported, through 2017.  CentOS and Debian-specific PHP releases are always maintained in this way, and are supported through the end of the OS lifecycle.

Choosing a Version of PHP

For the most part, we recommend that you do not change the version of PHP away from the default for your system configuration.  This is especially true if you are operating a shared hosting environment.  It's best to ensure a common, stable PHP version is in use to maximize compatibility with customer software.

We do not recommend ever running PHP 4.x in a production environment, as it has been end of life for several years.

If you are running your server in an environment where you are able to manage all the applications and you have one or more that require or strongly recommend a specific version of PHP, or if you are developing your own application and would like to use features from a specific version of PHP, it makes sense to adjust accordingly.

For technical reasons, official support for PHP from Steadfast is the same as what appears in the above table.  Limited "best effort" assistance is often available for increasing the PHP version to something newer than the table indicates.  We currently recommend against PHP 5.5 unless it is provided by your system, because it is a relatively new PHP release.  Many applications do not yet support the differences from PHP 5.4 properly.

When you choose to add LiteSpeed Web Server to an existing Linux server configuration, our recommendation is to match the OS version of PHP so that scheduled tasks and command-line scripts run using the same version of PHP as the web server uses.  However, as long as your applications do not experience trouble using a newer version of PHP, there is no problem with doing this, and it is a supported configuration.

Also noted in the table above is that some configurations include multiple versions of PHP by default.  If your system is configured in this way, you can configure each site or application to use a different version of PHP as you like.  This is a feature available for Microsoft Windows IIS Web Server, and for Plesk servers.

Differences between PHP Versions

The differences between each version of PHP are too extensive to list here, but mostly involve new or deprecated functionality for PHP scripts.  Most scripts will support a minimum PHP version and then deal with the differences in newer versions automatically, or gain extra features in newer versions as appropriate.

If you are not familiar with writing PHP scripts, it is best to follow the system requirement guidelines of your applications and reasonably safe to disregard the specific differences between any two PHP versions.

If you are interested in technical differences, the PHP 5 Change Log describes all modifications made in each version of PHP.

Getting Help

If you have any questions about supported versions of PHP for your environment or changing between them, our support team will be happy to help you determine your options and configure your server to support the version you need.  Feel free to contact us for help.