fix: is_cli() returns true when $_SERVER['HTTP_USER_AGENT'] is missing

Fixes #5336

Author: kenjis

system/Common.php

@@ -643,16 +643,7 @@ function helper($filenames)
      */
     function is_cli(): bool
     {
-        if (defined('STDIN')) {
-            return true;
-        }
-
-        if (! isset($_SERVER['REMOTE_ADDR'], $_SERVER['HTTP_USER_AGENT']) && isset($_SERVER['argv']) && count($_SERVER['argv']) > 0) {
-            return true;
-        }
-
-        // if source of request is from CLI, the `$_SERVER` array will not populate this key
-        return ! isset($_SERVER['REQUEST_METHOD']);
+        return in_array(PHP_SAPI, ['cli', 'phpdbg'], true);
     }
 }