Serve file to user over http via php

问题

If I goto http://site.com/uploads/file.pdf I can retrieve a file.

However, if I have a script such as:

<?php 

ini_set('display_errors',1);
error_reporting(E_ALL|E_STRICT);

//require global definitions 
require_once("includes/globals.php"); 
//validate the user before continuing 
isValidUser(); 
$subTitle = "Attachment";   
$attachmentPath = "/var/www/html/DEVELOPMENT/serviceNow/selfService/uploads/";
if(isset($_GET['id']) and !empty($_GET['id'])){
    //first lookup attachment meta information 
    $a = new Attachment(); 
    $attachment = $a->get($_GET['id']); 
    //filename will be original file name with user name.n prepended 
    $fileName = $attachmentPath.$_SESSION['nameN'].'-'.$attachment->file_name; 
    //instantiate new attachmentDownload and query for attachment chunks 
    $a = new AttachmentDownload(); 
    $chunks= $a->getRecords(array('sys_attachment'=>$_GET['id'], '__order_by'=>'position')); 


    $fh = fopen($fileName.'.gz','w');                                                      
    // read and base64 encode file contents 
    foreach($chunks as $chunk){
            fwrite($fh, base64_decode($chunk->data));   
    }
    fclose($fh);

    //open up filename for writing 
    $fh = fopen($fileName,'w');     
    //open up filename.gz for extraction                                
    $zd = gzopen($fileName.'.gz', "r");
    //iterate over file and write contents 
    while (!feof($zd)) {
            fwrite($fh, gzread($zd, 60*57));    
    }
    fclose($fh); 
    gzclose($zd);
    unlink($fileName.'.gz'); 
    $info = pathinfo($fileName); 

    header('Content-Description: File Transfer');
    header('Content-Type: '.Mimetypes::get($info['extension']));
    header('Content-Disposition: attachment; filename=' . basename($fileName));
    header('Content-Transfer-Encoding: binary');
    header('Expires: 0');
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    header('Pragma: public');
    header('Content-Length: ' . filesize($fileName));
    ob_clean();
    flush();
    readfile($fileName);
    exit();
}else{
    header("location: ".$links['status']."?".urlencode("item=incident&action=view&status=-1&place=".$links['home']));   
}


?>

This results in sending me the file, but when I open it I receive an error saying:

"File type plain text document (text/plain) is not supported"

回答1:

First off, I'd start by checking the HTTP headers. You can do this in Firefox easily using the "Live HTTP headers" extension; not sure about equivalents in other browsers offhand. This will let you verify if the header is actually getting set to "application/pdf" and whether your other headers are getting set as well.

If none of the headers are getting set, you might be inadvertently sending output before the calls to header(). Is there any whitespace before the <?php tag?

回答2:

Are you sure application/pdf is the header your browser is actually seeing?

You can check that out with various HTTP dev tools, for instance HTTP Client for the Mac or Firebug for Firefox.

回答3:

I use this one and it works.

if(file_exists($file_serverfullpath))
{    
   header("Pragma: public");
   header("Expires: 0");
   header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
   header("Cache-Control: private", false);

   //sending download file
   header("Content-Type: application/octet-stream"); //application/octet-stream is more generic it works because in now days browsers are able to detect file anyway
   header("Content-Disposition: attachment; filename=\"" . basename($file_serverfullpath) . "\""); //ok
   header("Content-Transfer-Encoding: binary");
   header("Content-Length: " . filesize($file_serverfullpath)); //ok
   readfile($file_serverfullpath);
}

回答4:

Try prepending "error_reporting(0);". I found this in the comments at http://php.net/readfile (where you took this example from).

Another thing that could be a problem is your file size. There have been issues reported in the past about PHP5 (we're talking 2005 here, so i hope this is fixed by now) having trouble reading files >2MB. If your file size exceeds this you may want to verify that it reads the whole file.

来源：https://stackoverflow.com/questions/3610746/serve-file-to-user-over-http-via-php