php下载文件的一种方式

<?php

ob_start();  

// $file_name="cookie.jpg";
$file_name="abc.jpg";

//用以解决中文不能显示出来的问题
$file_name=iconv("utf-8","gb2312",$file_name);
//$file_sub_path=$_SERVER['DOCUMENT_ROOT']."marcofly/phpstudy/down/down/";
$file_sub_path=$_SERVER['DOCUMENT_ROOT'];
$file_path=$file_sub_path.$file_name;
//首先要判断给定的文件存在与否
if(!file_exists($file_path)){
echo "没有该文件文件";
return ;
}
$fp=fopen($file_path,"r");
$file_size=filesize($file_path);
//下载文件需要用到的头
ob_end_clean();

Header("Content-type: application/octet-stream");
//Header("Content-type: image/jpeg");
Header("Accept-Ranges: bytes");
Header("Accept-Length:".$file_size);
//Header("Content-Disposition: attachment; filename=".basename($file_name));
 Header("Content-Disposition: attachment; filename=".$file_name);
$buffer=1024;
$file_count=0;
//向浏览器返回数据
while(!feof($fp) && $file_count<$file_size){
$file_con=fread($fp,$buffer);
$file_count+=$buffer;
echo $file_con;
}
@fclose($fp); 

exit(0);  

 /*
第二种方法
*/
/*
ob_start();
$file_name="123.jpg";
$file_name = iconv("utf-8","gb2312",$file_name);
if (!is_file($file_name)){
    echo "url error!";
} else {
    $ua = $_SERVER["HTTP_USER_AGENT"];
    if (preg_match("/MSIE/", $ua)) {
        $encoded_filename = urlencode(basename($file_name));
        $encoded_filename = str_replace("+", "%20", $encoded_filename);
        $con_dis = 'Content-Disposition: attachment; filename="' . $encoded_filename . '"';
    } else if (preg_match("/Firefox/", $ua)) {
        $con_dis = 'Content-Disposition: attachment; filename*="utf8\'\'' . basename($file_name) . '"';
    } else {
        $con_dis = 'Content-Disposition: attachment; filename="' . basename($file_name) . '"';
    }
    $file = fopen($file_name, "r");
    //输入文件标签
    ob_end_clean();Header("Content-type: application/octet-stream");Header("Accept-Ranges: bytes");Header("Accept-Length: ".filesize($file_name));Header($con_dis);
    //输出文件内容
    //读取文件内容并直接输出到浏览器
    echo fread($file, filesize($file_name));@fclose($file);
    exit(0);
}
*/
/*
echo $_SERVER["HTTP_USER_AGENT"];
echo "<br/>";
echo $_SERVER['DOCUMENT_ROOT'];
*/
?>