Xhprof graphviz Warning: proc_open() [function.proc-open]: CreateProcess failed, error code 解決方法

Xhprof在windows下點擊[View Full Callgraph]調用graphviz軟件時。
警告Warning: proc_open() [function.proc-open]: CreateProcess failed, error code – 0 in
並提示
failed to execute cmd " D:/graphviz-2.38/release/bin/dot -Tpng"

位置是xhprof_lib/utils/callgraph_utils.php文件下xhprof_generate_image_by_dot函數
windows下
$cmd = " dot -T".$type;
需要替換成
$cmd = " D:/graphviz-2.38/release/bin/dot -T".$type;

問題就出現在這行代碼
$process = proc_open($cmd, $descriptorspec, $pipes, "/tmp", array());
需要改成
$process = proc_open($cmd, $descriptorspec, $pipes);

或者是建立相應的tmp文件夾，因為默認是不存在tmp文件夾的。嘗試在網站根目錄建立tmp文件夾但是還是保存，於是改成了在當前目錄。
$process = proc_open($cmd, $descriptorspec, $pipes, "tmp", array());

//修改后的正確代碼

function xhprof_generate_image_by_dot($dot_script, $type) {
    //echo($dot_script);
  $descriptorspec = array(
       // stdin is a pipe that the child will read from
       0 => array("pipe", "r"),
       // stdout is a pipe that the child will write to
       1 => array("pipe", "w"),
       // stderr is a pipe that the child will write to
       2 => array("pipe", "w")
       );

  //$cmd = " dot -T".$type; //linux下
  //1.修改graphviz目錄
  $cmd = " D:/graphviz-2.38/release/bin/dot -T".$type;//windows下
  //2.tmp文件夾處理
  $process = proc_open($cmd, $descriptorspec, $pipes);
  if (is_resource($process)) {
    fwrite($pipes[0], $dot_script);
    fclose($pipes[0]);

    $output = stream_get_contents($pipes[1]);

    $err = stream_get_contents($pipes[2]);
    if (!empty($err)) {
      print "failed to execute cmd: \"$cmd\". stderr: `$err'\n";
      exit;
    }

    fclose($pipes[2]);
    fclose($pipes[1]);
    proc_close($process);
    return $output;
  }
  print "failed to execute cmd \"$cmd\"";
  exit();

　　

}