php通过文件流方式复制文件的方法

<?php 
  function stream_copy($src, $dest) 
  { 
    $fsrc = fopen($src,'r'); 
    $fdest = fopen($dest,'w+'); 
    $len = stream_copy_to_stream($fsrc,$fdest); 
    fclose($fsrc); 
    fclose($fdest); 
    return $len; 
  } 
?>