In Plesk Interface some PHP versions are marked as 'outdated'. What does it mean?
'Outdated' mark next to some of PHP versions was introduced in Plesk Onyx 17.8.
This mark means that the PHP version has reached its End-of-Life.
Versions of PHP marked as outdated are: 5.2.X, 5.3.X, 5.4.X, 5.5.X, 5.6.X, and 7.0.X. Refer to the official PHP website for more details: https://php.net/supported-versions.php.
These versions are still available for installation via Plesk Installer and can be enabled on a website on one's own risk.
Note: It is not possible to hide 'Outdated' mark as these settings are hard-coded.