php-protobuf had the same bug with empty comments as pb4php...

src/php-protobuf/ProtobufCompiler/ProtobufParser.php

@@ -1209,7 +1209,7 @@ private function _getBeginEnd($string, $char, $charend)
      */
     private function _stripComments(&$string)
     {
-        $string = preg_replace('/\/\/.+/', '', $string);
+        $string = preg_replace('/\/\/.*/', '', $string);
         // now replace empty lines and whitespaces in front
         $string = preg_replace('/\\r?\\n\s*/', PHP_EOL, $string);
     }