两段相似代码 后一个为什么不能执行呢

escil

[php]

function MyCounter() {
  $counterFile="/tmp";  //后一个是在此处进行了修改
  if (!file_exists($counterFile)) {
          if (!file_exists(dirname($counterFile))) {
      mkdir(dirname($counterFile), 0700);
    }
    exec("echo 0 > $counterFile");
  }
  $fp = fopen($counterFile,"rw");
  $num = fgets($fp,5);
  $num += 1;
  print "$num";
  echo $counterFile;
  exec("rm -rf $counterFile");
  exec("echo $num > $counterFile");
}
[/php]







[php]

function MyCounter() {
  $counterFile="/tmp/a.txt";
  if (!file_exists($counterFile)) {
          if (!file_exists(dirname($counterFile))) {
      mkdir(dirname($counterFile), 0700);
    }
    exec("echo 0 > $counterFile");
  }
  $fp = fopen($counterFile,"rw");
  $num = fgets($fp,5);
  $num += 1;
  print "$num";
  echo $counterFile;
  exec("rm -rf $counterFile");
  exec("echo $num > $counterFile");
}
[/php]

escil

前一个代码执行后
在本磁盘的根目录建立了一个tmp文件（是文件不是目录）

后一个执行后就说
Your are the  <br />
<b>Warning</b>:  fopen(/tmp/a.txt) [<a href='function.fopen'>function.fopen</a>]: failed to open stream: No such file or directory in <b>D:\Program Files\Apache Group\Apache2\htdocs\zend\index2.php</b> on line <b>17</b><br />
<br />
<b>Warning</b>:  fgets(): supplied argument is not a valid stream resource in <b>D:\Program Files\Apache Group\Apache2\htdocs\zend\index2.php</b> on line <b>18</b><br />
1/tmp/a.txtguest