Short open code converts to comments (no replies)

I have wampserver 3.2.0 and for some compatibility with an old code I need to use Php 5.6.40

All fine, works great

The only issue is that the code uses short open tags and when apache/php reads them, it converts to html comments

I want to display a warning/error instead

Not an option to just replace short open tags with long tags. Really need to stop the script or at least warning/error