We are extending security support for the Magento2.3.x release line for an additionalthree months (through April 2022).Considering that support for PHP 7.3 ends in December 2021, we will be introducing PHP 7.4 compatibilityto the release of Magento Commerce and Magento Open Source 2.3.7 in May 2021.For compliance reasons, we encourage all merchants to upgrade to PHP 7.4 before December 2021 - even those still using Magento 2.3.While Magento 2.3.7 and later 2.3.x versions will still be compatible with PHP 7.3, Adobe will not be testing with PHP 7.3, nor will Adobe release any fixes for PHP 7.3. Given that Magento 2.4.x already supports PHP 7.4, with the Magento 2.3.7 release,both 2.3.x and 2.4.x will have PHP 7.4 as the recommended PHP version.
Magento 2.3.7 introducesbackward incompatible changeswhich need to be consideredby anyone who has not yet upgraded to Magento 2.4. Migration from PHPUnit 6 to PHPUnit 9 (which is what occurred for Magento 2.4.0) is one such change, as it affectsthe following types of tests:
Magento Marketplace extension vendors should ensure their extensions are compatible with PHP 7.4 when publishing new versions for Magento 2.3.7 and later. Merchants should thoroughly test and evaluate their store before running a live site on PHP 7.4.
While added support for PHP7.4 in the 2.3.x release line will help ensure PHP compatibility through the life of Magento 2.3, we still recommend you evaluate and prioritize an upgrade to Magento 2.4. This will ensure that your organization is positioned for long-term success with the latest, most secure version of Magento.