我看中文手册上的计数器,可传到网站上后,实现不了,有一点也没看明白,请高手帮忙看一下,代码如下:





<?php
$counterFile = "/tmp/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( "rm -rf $counterFile");
exec( "echo $num > $counterFile");
}

if (!file_exists($counterFile)) {
exec( "echo 0 > $counterFile");
}

displayCounter($counterFile);

?>


这两句我看不太明白,不知道什么意思
exec( "rm -rf $counterFile");
exec( "echo $num > $counterFile");
请指教!