这个函数参数起啥作用?

我怎么没感觉到它没起作用啊?就是这个"$punctuation"小弟新手,代码:
<html>
<body><?php
function writeMyName($fname,$punctuation)
  {
  echo $fname . " Yang" . $punctuation . "<br />";
  }echo "My name is ";
writeMyName("David",".");echo "My name is ";
writeMyName("Mike","!");echo "My name is ";
writeMyName("John","...");
?>
</body>
</html>