大家看看啊这个是我在书上看的简单计数器，有个问题就是 exec( "echo $num > $counterFile");这个语句是怎么用的啊，要写进文件必须要用这样形式吗，特别是＞是如何用的啊？　谢谢大家一起讨论指教．
$counterFile = "D:\usr\www\html\class\counter.txt";

function displayCounter($counterFile) {
$fp = fopen($counterFile,"rw");
$num = fgets($fp,5);
$num += 1;
print "您是第 "."$num"." 位无聊份子";
exec( "echo $num > $counterFile");
}


displayCounter($counterFile);