PHP实现的文件操作类及文件下载功能示例

<?php
 // copyright 2005, lee babin (lee@thecodeshoppe.com)
 // this code may be used and redistributed without charge
 // under the terms of the gnu general public
 // license version 2.0 or later -- www.gnu.org
 // subject to the retention of this copyright
 // and gpl notice in all copies or derived works
 class cfile {
  //the path to the file we wish to work with.
  protected $thepath;
  //error messages in the form of constants for ease of use.
  const founderror = "sorry, the file in question does not exist.";
  const permerror = "sorry, you do not have the proper permissions on this file";
  const openerror = "sorry, the file in question could not be opened.";
  const closeerror = "sorry, the file could not be closed.";
  //the constructor function.
  public function __construct (){
   $num_args = func_num_args();
   if($num_args > 0){
    $args = func_get_args();
    $this->thepath = $args[0];
   }
  }
  //a function to open the file.
  private function openfile ($readorwrite){
    //first, ensure the file exists.
    try {
      if (file_exists ($this->thepath)){
        //now, we need to see if we are reading or writing or both.
        $proceed = false;
        if ($readorwrite == "r"){
          if (is_readable($this->thepath)){
            $proceed = true;
          }
        } elseif ($readorwrite == "w"){
          if (is_writable($this->thepath)){
            $proceed = true;
          }
        } else {
          if (is_readable($this->thepath) && is_writable($this->thepath)){
            $proceed = true;
          }
        }
        try {
          if ($proceed){
            //we can now attempt to open the file.
            try {
              if ($filepointer = fopen ($this->thepath, $readorwrite)){
                return $filepointer;
              } else {
                throw new exception (self::openerror);
                return false;
              }
            } catch (exception $e) {
              echo $e->getmessage();
            }
          } else {
            throw new exception (self::permerror);
          }
        } catch (exception $e) {
          echo $e->getmessage();
        }
      } else {
        throw new exception (self::founderror);
      }
    } catch (exception $e) {
      echo $e->getmessage();
    }
  }
  //a function to close a file.
  function closefile () {
    try {
      if (!fclose ($this->thepath)){
        throw new exception (self::closeerror);
      }
    } catch (exception $e) {
      echo $e->getmessage();
    }
  }
  //a function to read a file, then return the results of the read in a string.
  public function read () {
    //first, attempt to open the file.
    $filepointer = $this->openfile ("r");
    //now, return a string with the read data.
    if ($filepointer != false){
      //then we can read the file.
      return fgets ($filepointer);
    }
    //lastly, close the file.
    $this->closefile ();
  }
  //a function to write to a file.
  public function write ($towrite) {
    //first, attempt to open the file.
    $filepointer = $this->openfile ("w");
    //now, return a string with the read data.
    if ($filepointer != false){
      //then we can read the file.
      return fwrite ($filepointer, $towrite);
    }
    //lastly, close the file.
    $this->closefile ();
  }
  //a function to append to a file.
  public function append ($toappend) {
    //first, attempt to open the file.
    $filepointer = $this->openfile ("a");
    //now, return a string with the read data.
    if ($filepointer != false){
      //then we can read the file.
      return fwrite ($filepointer, $toappend);
    }
    //lastly, close the file.
    $this->closefile ();
  }
  //a function to set the path to a new file.
  public function setpath ($newpath) {
    $this->thepath = $newpath;
  }
 }
?>

<?php
  $myfile = new cfile ("test.txt");
  //now, let's try reading it.
  echo $myfile->read();
  //then let's try writing to the file.
  $myfile->write ("hello world!");
  //then, let's try appending.
  $myfile->append ("hello again!");
?>

<?php
$filename = 'file1.txt';
$file = fopen($filename, 'r');
header("expires: 0");
header("pragma: public");
header("cache-control: must-revalidate, post-check=0, pre-check=0");
header("cache-control: public");
header("content-length: ". filesize($filename));
header("content-type: application/octet-stream");
header("content-disposition: attachment; filename=".$filename);
readfile($filename);
?>