The Cloud Client Libraries for PHP are compatible with at least the three most recent, major PHP releases. This means that the PHP client libraries are compatible with all actively supported PHP releases. PHP releases a new major version every 12 months, with two active versions and one version receiving security fixes only.
For example, if the current Cloud Client Libraries for PHP release is PHP 8.1, the client libraries are compatible with PHP 8.1, PHP 8.0, and PHP 7.4. The libraries will always be compatible with at least one GA runtime for App Engine and Cloud Functions. For more information, see Client libraries explained.
For new development
When starting a new project for new development, we recommend that you use the current release of PHP. This ensures that your runtime uses a supported PHP release and receives critical security patches.
Keeping production systems current
Keeping your production systems on supported PHP versions is the best way to ensure that you receive critical security and bug fixes. When Cloud Client Libraries for PHP increment a minor version they may drop compatibility with a previous PHP version. When a new version of a library becomes available that drops support for a PHP version, consider upgrading your runtime to the latest version of PHP. For more information about the use of major and minor versions, see Semantic Versioning.
Where to find version information
To find out what PHP versions are supported, see the Google Cloud Client Libraries for PHP page.