diff --git a/html-minifier.php b/html-minifier.php
index 9c44a29..9373db0 100644
--- a/html-minifier.php
+++ b/html-minifier.php
@@ -17,6 +17,8 @@
 
 require_once $autoload;
 
+version_compare($ver = PHP_VERSION, $req = '7.1.3', '<') and exit(sprintf('You are running PHP %s, but plugin needs at least <strong>PHP %s</strong> to run.', $ver, $req));
+
 class HtmlMinifier {
 
     private static array $options = [];