Support

The minimum PHP requirement for Akeeba Backup 7.2 is PHP 7.1. The fact that the minimum requirements changed was communicated in the Release Notes which are also displayed when Joomla detects the update. Here's the very top item of that page:

Minimum requirements raised to PHP 7.1, Joomla 3.9. In an effort to support the upcoming Joomla 4.0 we had to do major and far-reaching changes to our software. Some of the necessary changes were impossible while supporting older PHP versions such as 5.6 and 7.0 – versions of PHP which have been end of life for well over a year. As noted, we consider versions of PHP which went EOL over six months ago to be good candidates for removal. Further to that, our usage statistics show that less than 5% of total sites and less than 0.5% of current Joomla version sites use them, therefore we decided to drop support. On a similar note, Joomla versions lower than or equal to 3.8 represent less than 2% of the Joomla sites of our users so we decided to drop support for them to make it possible to prepare our software for Joomla 4.

Moreover, if you're even in doubt, please refer to our Compatibility page. This page is generated automatically from the compatibility information tagged with each release, taking into account each Joomla version's minimum requirement as well.