I’m using WordPress version 4.9.8 and my PHP version is above 5.6. Even if my installation didn’t meet the minimum requirements, your plugin should fail more gracefully than causing the site to hang. Do your version checks before the rest of your code executes.
I changed my review to 3 stars because I was mostly just angry when I left my review and I don’t like leaving 1 stars unless the plugin is exceptionally terrible.