Hi @postas - thanks for getting in touch! You could continue using your server’s current version of PHP, however we would not be able to offer as much support as we do for folks using our PHP Library. You would have to build your app’s API functionality directly if you continue to use 7.2.5. The official Shopify PHP API library does require PHP version 7.3+ as a dependency if you wanted to go that route. There is a bit more information on this here.
Hope this helps - please let me know if we can clarify anything further on our end.