php 下载文件的代码分享

在php中实现下载文件，方法大多是如下二种：
一种是使用system、exec等即有的函数调用系统自带的下载工具，比如 wget 之类的来下载文件。
另一种是使用php本身利用Socket来下载文件。

笔者喜欢用第二种方式。

使用Socket下载文件，如果是http协议的文件，必须明白HTTP协议的运行过程，如果是FTP协议的则要了解ftp协议运行过程。
比如HTTP协议访问一个文件：

<?php
$fp = fsockopen("www.example.com", 80, $errno, $errstr, 30);
if (!$fp) {
        echo "$errstr ($errno)<br />n";
} else {
    $out = "GET / HTTP/1.1rn";
    $out .= "Host: www.example.comrn";
    $out .= "Connection: Closernrn";

    fwrite($fp, $out);
        while (!feof($fp)) {
            echo fgets($fp, 128);
        }
    fclose($fp);
}
?>

使用fopen直接访问远程文件来达到目的，同时又可以访问http，也能访问ftp。
当然，如果按照上面的思路来说，也可以使用ftp的函数库来实现。

使用fopen函数的例子：

#! /usr/bin/php
<?php
error_reporting(0);
set_time_limit(0);

//无参数则给出提示
if ($argc < 2){
  echo "Usage: ". $argv[0] ." URL [Destination]nn";
  exit();
}

//设置获取基本变量
$url = $argv[1];
$save_path = $argv[2] ? $argv[2] : "./";
$file_name = array_pop(explode("/", $url));
$localfile = $save_path . $file_name;

//检查变量
if (!check_url($url)){
   exit("Error: URL ". $url ." invalid.nn");
}
if (file_exists($localfile)){
   exit("Error: local file ". $localfile ." exists.nn");
}

//打开远程文件
$fp = fopen($url, "rb");
if (!$fp){
   exit("Error: Download ". $url ." failed.nn");
}

//打开本地文件
$sp = fopen($localfile, "wb");
if (!$sp){
   exit("Error: Open local file ". $localfile ." failed.nn");
}

//下载远程文件
echo "Downloading, please waiting...nn";
while (!feof($fp)){
    $tmpfile .= fread($fp, 1024);
}

//保存文件到本地
fwrite($sp, $tmpfile);
fclose($fp);
fclose($sp);
echo "Download file ". $file_name ." succeed!nn";

/* 检查URL合法性函数 */
function check_url($url){
   return preg_match("/^(http|ftp)(://)([a-zA-Z0-9-_]+[./]+[w-_/]+.*)+$/i", $url);    
}
?>

以上代码保存为 download.php 文件，加上可执行属性：
chmod +x download.php

执行，注意脚本的路径要正确：
#! /usr/local/php/bin/php

使用上面的脚本来下载文件：
download.php 远程文件      保存路径

如把Google Talk程序下载到我们的 /tmp 目录下：
download.php  http://dl.google.com/googletalk/googletalk-setup.exe /tmp/

如果不出错，等待一会就能够在 /tmp/ 目录下看到 googletalk-setup.exe 文件。

这里分享一个更强的HTTP下载类:

<?
/*=================
// 织梦Http下载类
=======================*/
class DedeHttpDown
{
var $m_url = "";
var $m_urlpath = "";
var $m_scheme = "http";
var $m_host = "";
var $m_port = "80";
var $m_user = "";
var $m_pass = "";
var $m_path = "/";
var $m_query = "";
var $m_fp = "";
var $m_error = "";
var $m_httphead = "" ;
var $m_html = "";
//
//初始化系统
//
function PrivateInit($url)
{
      $urls = "";
      $urls = @parse_url($url);
      $this->m_url = $url;
        if(is_array($urls))
        {
        $this->m_host = $urls["host"];
        if(!empty($urls["scheme"])) $this->m_scheme = $urls["scheme"];
     
        if(!empty($urls["user"])){
        $this->m_user = $urls["user"];
        }
     
        if(!empty($urls["pass"])){
        $this->m_pass = $urls["pass"];
        }

        if(!empty($urls["port"])){
        $this->m_port = $urls["port"];
        }
     
        if(!empty($urls["path"])) $this->m_path = $urls["path"];
        $this->m_urlpath = $this->m_path;
     
        if(!empty($urls["query"]))
        {
        $this->m_query = $urls["query"];
        $this->m_urlpath .= "?".$this->m_query;
        }
     }
}
//
//打开指定网址
//
function OpenUrl($url)
{
     //重设各参数
     $this->m_url = "";
     $this->m_urlpath = "";
     $this->m_scheme = "http";
     $this->m_host = "";
     $this->m_port = "80";
     $this->m_user = "";
     $this->m_pass = "";
     $this->m_path = "/";
     $this->m_query = "";
     $this->m_error = "";
     $this->m_httphead = "" ;
     $this->m_html = "";
     $this->Close();
     //初始化系统
     $this->PrivateInit($url);
     $this->PrivateStartSession();
}
//
//获得某操作错误的原因
//
function printError()
{
     echo "错误信息：".$this->m_error;
     echo "具体返回头：<br>";
     foreach($this->m_httphead as $k=>$v)
     { echo "$k => $v <br>rn"; }
}
//
//判别用Get方法发送的头的应答结果是否正确
//
function IsGetOK()
{
     if( ereg("^2",$this->GetHead("http-state")) )
     { return true; }
     else
     {
      $this->m_error .= $this->GetHead("http-state")." - ".$this->GetHead("http-describe")."<br>";
      return false;
     }
}
//
//看看返回的网页是否是text类型
//
function IsText()
{
     if(ereg("^2",$this->GetHead("http-state"))
      && eregi("^text",$this->GetHead("content-type")))
     { return true; }
     else
     {
      $this->m_error .= "内容为非文本类型<br>";
      return false;
     }
}
//
//判断返回的网页是否是特定的类型
//
function IsContentType($ctype)
{
     if(ereg("^2",$this->GetHead("http-state"))
      && $this->GetHead("content-type")==strtolower($ctype))
     { return true; }
     else
     {
      $this->m_error .= "类型不对 ".$this->GetHead("content-type")."<br>";
      return false;
     }
}
//
//用Http协议下载文件
//
function SaveToBin($savefilename)
{
     if(!$this->IsGetOK()) return false;
     if(@feof($this->m_fp))
     { $this->m_error = "连接已经关闭！"; return false; }
     $fp = fopen($savefilename,"w") or die("写入文件 $savefilename 失败！");
     while(!feof($this->m_fp)){
      @fwrite($fp,fgets($this->m_fp,256));
     }
     @fclose($this->m_fp);
     return true;
}
//
//保存网页内容为Text文件
//
function SaveToText($savefilename)
{
     if($this->IsText()) $this->SaveBinFile($savefilename);
     else return "";
}
//
//用Http协议获得一个网页的内容
//
function GetHtml()
{
     if(!$this->IsText()) return "";
     if($this->m_html!="") return $this->m_html;
     if(!$this->m_fp||@feof($this->m_fp)) return "";
     while(!feof($this->m_fp)){
      $this->m_html .= fgets($this->m_fp,256);
     }
     @fclose($this->m_fp);
     return $this->m_html;
}
//
//开始HTTP会话
//
function PrivateStartSession()
{
     if(!$this->PrivateOpenHost()){
      $this->m_error .= "打开远程主机出错!";
      return false;
     }
     if($this->GetHead("http-edition")=="HTTP/1.1") $httpv = "HTTP/1.1";
     else $httpv = "HTTP/1.0";
     fputs($this->m_fp,"GET ".$this->m_urlpath." $httpvrn");
     fputs($this->m_fp,"Host: ".$this->m_host."rn");
     fputs($this->m_fp,"Accept: */*rn");
     fputs($this->m_fp,"User-Agent: Mozilla/4.0+(compatible;+MSIE+6.0;+Windows+NT+5.2)rn");
     //HTTP1.1协议必须指定文档结束后关闭链接,否则读取文档时无法使用feof判断结束
     if($httpv=="HTTP/1.1") fputs($this->m_fp,"Connection: Closernrn");
     else fputs($this->m_fp,"rn");
     $httpstas = fgets($this->m_fp,256);
     $httpstas = split(" ",$httpstas);
     $this->m_httphead["http-edition"] = trim($httpstas[0]);
     $this->m_httphead["http-state"] = trim($httpstas[1]);
     $this->m_httphead["http-describe"] = "";
     for($i=2;$i<count($httpstas);$i++){
      $this->m_httphead["http-describe"] .= " ".trim($httpstas[$i]);
     }
     while(!feof($this->m_fp)){
      $line = str_replace(""","",trim(fgets($this->m_fp,256)));
      if($line == "") break;
      if(ereg(":",$line)){
       $lines = split(":",$line);
       $this->m_httphead[strtolower(trim($lines[0]))] = trim($lines[1]);
      }
     }
}
//
//获得一个Http头的值
//
function GetHead($headname)
{
     $headname = strtolower($headname);
     if(isset($this->m_httphead[$headname]))
      return $this->m_httphead[$headname];
     else
      return "";
}
//
//打开连接
//
function PrivateOpenHost()
{
     if($this->m_host=="") return false;
     $this->m_fp = @fsockopen($this->m_host, $this->m_port, &$errno, &$errstr,10);
     if(!$this->m_fp){
      $this->m_error = $errstr;
      return false;
     }
     else{
      return true;
     }
}
//
//关闭连接
//
function Close(){
     @fclose($this->m_fp);
}
}
?>

调用示例：
1，下载网页

<?
$httpdown = new DedeHttpDown();
$httpdown->OpenUrl("http://www.jb200.com");
echo $httpdown->GetHtml();
$httpdown->Close();
?>

2，下载图片并保存

<?
$httpdown = new DedeHttpDown();
$httpdown->OpenUrl("http://img.jb200.com/images/1.jpg");
echo $httpdown->SaveBin("test.jpg");
$httpdown->Close();
echo "<img src='test.jpg'>";
?>