is_uploaded_file()

(PHP 4 >= 4.0.3, PHP 5, PHP 7)

判断文件是否是通过 HTTP POST 上传的

说明

is_uploaded_file(string $filename): bool

如果$filename所给出的文件是通过 HTTP POST 上传的则返回TRUE。这可以用来确保恶意的用户无法欺骗脚本去访问本不能访问的文件，例如/etc/passwd。

这种检查显得格外重要，如果上传的文件有可能会造成对用户或本系统的其他用户显示其内容的话。

为了能使is_uploaded_file()函数正常工作，必段指定类似于$_FILES['userfile']['tmp_name']的变量，而在从客户端上传的文件名$_FILES['userfile']['name']不能正常运作。

参数

$filename

要检查的文件名。

返回值

成功时返回TRUE，或者在失败时返回FALSE。

范例

Example #1is_uploaded_file()例子

<?php
if (is_uploaded_file($_FILES['userfile']['tmp_name'])) {
   echo "File ". $_FILES['userfile']['name'] ." uploaded successfully.\n";
   echo "Displaying contents\n";
   readfile($_FILES['userfile']['tmp_name']);
} else {
   echo "Possible file upload attack: ";
   echo "filename '". $_FILES['userfile']['tmp_name'] . "'.";
}
?>

参见

• move_uploaded_file() 将上传的文件移动到新位置
• $_FILES
• 关于用法的简单例子文件上传处理

Note that calling this function before move_uploaded_file() is not necessary, as it does the exact same checks already. It provides no extra security. Only when you're trying to use an uploaded file for something other than moving it to a new location.
Reference:
https://github.com/php/php-src/blob/master/ext/standard/basic_functions.c#L5796

As of PHP 4.2.0, rather than automatically assuming a failed file uploaded is a file attack, you can use the error code associated with the file upload to check and see why the upload failed. This error code is stored in the userfile array (ex: $HTTP_POST_FILES['userfile']['error']). 
Here's an example of a switch:
if (is_uploaded_file($userfile)) {
 
 //include code to copy tmp file to final location here...
 
}else{
 switch($HTTP_POST_FILES['userfile']['error']){
  case 0: //no error; possible file attack!
   echo "There was a problem with your upload.";
   break;
  case 1: //uploaded file exceeds the upload_max_filesize directive in php.ini
   echo "The file you are trying to upload is too big.";
   break;
  case 2: //uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the html form
   echo "The file you are trying to upload is too big.";
   break;
  case 3: //uploaded file was only partially uploaded
   echo "The file you are trying upload was only partially uploaded.";
   break;
  case 4: //no file was uploaded
   echo "You must select an image for upload.";
   break;
  default: //a default error, just in case! :)
   echo "There was a problem with your upload.";
   break;
}
Additionally, by testing the 'name' element of the file upload array, you can filter out unwanted file types (.exe, .zip, .bat, etc). Here's an example of a filter that can be added before testing to see if the file was uploaded:
//rejects all .exe, .com, .bat, .zip, .doc and .txt files
if(preg_match("/.exe$|.com$|.bat$|.zip$|.doc$|.txt$/i", $HTTP_POST_FILES['userfile']['name'])){
 exit("You cannot upload this type of file.");
}
//if file is not rejected by the filter, continue normally
if (is_uploaded_file($userfile)) {
/*rest of code*/

To expand on what nicoSWD stated about this function.
Any script working with the temporary file $_FILES[]['tmp_name'] should call this function.
In any case where the script is modified to unlink(), rename() or otherwise modify the file that IS NOT move_uploaded_file() will not have the upload checked.
Likewise, most file operations are cached in PHP, therefore there should be minimal performance hit running is_uploaded_file before move_uploaded_file, since it will usually used a cached result for the latter.
The security benefits outweigh the microsecond difference in performance in any event, and should universally be used as soon as the $_FILES array is first entered into an application. While there may not be an immediate issue, code evolves and could quickly change this fact.

make use u got the enctype="multipart/form-data" in ur form tag otrherwise nothing works... took me two hours to find that out.......

Just looked at what I posted again and found several mistakes of the major and minor sort. That's what I get for posting before I finish my coffee. This should work better (i.e. should work in the first place):
<?php
  default: //a default error, just in case! :)
    echo "There was a problem with your upload.";
    $err_msg = "Unrecognized file POST error: ".$HTTP_POST_FILES['userfile']['error'];
    if (!(strpos($err_msg, "\n") === false)) {
      $err_lines = explode("\n", $err_msg);
      foreach ($err_lines as $msg) {
        error_log($msg, 0);
      }
    } else {
      error_log($err_msg, 0);
    }
    break;
?>

to get the example to work on windows, youll have to add a line, that replaces backslashes with slashes. eg.: $filename = str_replace ("\\", "/", $filename);
also, as someone mentioned, globalizing $HTTP_POST_FILES is a good idea ...
<pre>
/* Userland test for uploaded file. */
function is_uploaded_file($filename)
{
  global $HTTP_POST_FILES;
  if (!$tmp_file = get_cfg_var("upload_tmp_dir")) {
    $tmp_file = dirname(tempnam("", ""));
  }
  $tmp_file .= "/" . basename($filename);
  /* User might have trailing slash in php.ini... */
  // fix for win platform
  $filename = str_replace ("\\", "/", $filename);
  return (ereg_replace("/+", "/", $tmp_file) == $filename);
}
</pre>

The example brought out does not work as supposed to:
function is_uploaded_file($filename) {
  if (!$tmp_file = get_cfg_var('upload_tmp_dir')) {
    $tmp_file = dirname(tempnam('', ''));
  }
  $tmp_file .= '/' . basename($filename);
  /* User might have trailing slash in php.ini... */
  return (ereg_replace('/+', '/', $tmp_file) == $filename);
}
It works only with files under ....4 or 5 kb, other files automatically get the size of 0 bytes. So something must be wrong here. Built-in is_uploaded_file() works good.

Here is my code for file handler, i hope it help to all:
First a class to handler file upload:
<?php
  define('UPLOAD_PATH', 'upload/');
  define('MAXIMUM_FILESIZE', '10485760'); //10 MB
  class FileHandler
  {
    private $file_types = array('xls', 'xlsx');
    private $files = null;
    private $filename_sanitized = null;
    private $filename_original = null;
    
    
    public function __construct($files)
    {
      $this->files = $files;  
    }
    
    public function setFileTypes($fileTypes = array())
    {
      $this->file_types = $fileTypes;
      return $this;
    }
    
    public function setFileNameOriginal($filename)
    {
      $this->filename_original = $filename;
    }
    
    public function fileNameOriginal()
    {
      return $this->filename_original;
    }
    
    public function sanitize($cursor = 0)
    {
      $this->setFileNameOriginal($this->files['name'][$cursor]);
      
      $safe_filename = preg_replace(
          array("/\s+/", "/[^-\.\w]+/"),
          array("_", ""),
          trim($this->fileNameOriginal()));
      $this->filename_sanitized = md5($safe_filename.time()).$safe_filename;
      return $this;
    }
    
    public function fileSize($cursor = 0)
    {
      return $this->files['size'][$cursor];
    }
    
    public function extensionValid()
    {
      $fileTypes = implode('|', $this->file_types);
      $rEFileTypes = "/^\.($fileTypes){1}$/i";
      if(!preg_match($rEFileTypes, strrchr($this->filename_sanitized, '.')))
        throw new Exception('No se pudo encontrar el tipo de archivo apropiado');
      
      return $this;
    }
    
    public function isUploadedFile($cursor)
    {
      if(!is_uploaded_file($this->files['tmp_name'][$cursor]))
      {
        throw new Exception("No se obtuvo la carga del archivo");
      }
    }
    
    public function saveUploadedFile($cursor)
    {
      if(!move_uploaded_file ($this->files['tmp_name'][$cursor],UPLOAD_PATH.$this->filename_sanitized))
        throw new Exception("No se consigui&oacute; guardar el archivo");
    }
    
    public function fileNameSanitized()
    {
      return $this->filename_sanitized;
    }
    
    public function uploadFile($cursor = 0)
    {
      $this->isUploadedFile($cursor);
      if ($this->sanitize($cursor)->fileSize($cursor) <= MAXIMUM_FILESIZE)
      {
        $this->extensionValid() >saveUploadedFile($cursor);
      }
      else 
      {
        throw new Exception("El archivo es demasiado grande.");
      }
      return $name;      
    }
    
  }
?>
Next a part of code to use the class
<?php
//form is submited and detect that
if ($form_submited == 1)
{
  try
  {
        //i assume de input file is:
        /*
            <input id="<?php echo EXCEL_FILE;?>[]" name="<?php echo EXCEL_FILE;?>[]" type="file"/>
            where EXCEL_FILE is the constant: 
            define('EXCEL_FILE', 'excel_file');
        */
    $file = new FileHandler($_FILES['excel_file']);
    $inputFileName = $file->uploadFile() >fileNameSanitized(); // File to read
        ...
    
  }
  catch(Exception $e)
  {
    die('Error cargando archivo "'.($file->fileNameOriginal()).'": '.$e->getMessage());
  }
  
  
}
?>

Regarding the comment of info at metaltoad dot net
@ 19-Feb-2003 04:03
<?php
// ... yada yada yada...
preg_match("/.exe$|.com$|.bat$|.zip$|.doc$|.txt$/i", $HTTP_POST_FILES['userfile']['name']))
// ... yada yada yada...
?>
This will not work. It will, but not correctly.
You shuld escape the . (dot) for the preg function,
and escape the $ (dollar) sign for PHP, or use
single-quoted string...
The syntax should be (much shorter and neater):
<?php
// ... yada yada yada...
preg_match('/\\.(exe|com|bat|zip|doc|txt)$/i', $_FILES['userfile']['name']))
// ... yada yada yada...
?>

It isn't mentioned anywhere that I've seen, but $filename *is* case-sensitive on Windows.
It means that while C:\Windows\TEMP\php123.tmp may have been uploaded, C:\Windows\Temp\php123.tmp was not.
I found this out because I was using realpath() on the filename which 'fixed' the case (my Temp folder is in titlecase, not uppercase - thank you Vista).
Anyways, the problem was that PHP used %TEMP% to determine the destination for the uploaded file, and %TEMP% used the all-capitals version of the path. Changing it to use titlecase instead + restarting Apache fixed the problem.

If your $_FILES and $_POST are empty, this can be due to
- the limit set by post_max_size in php.ini
- the limit set by upload_max_filesize in php.ini
Unfortunately the first limit is not reported back as an error code in $_FILES['error'].

Regarding topcat's suggested change, I am split on doing that. I don't like showing users errors that may give them more information than they should have (or show that I haven't provided for that particular error). But I want to know when there are errors that fall to the default case so I can fix my code. What I will typically do is write them to the error log something like this modification to metaltoad's post (takes into account the possibility of multi-line errors which error_log doesn't handle well):
<?php
  default: //a default error, just in case! :)
    echo "There was a problem with your upload.";
    $err_msg = "Unrecognized file POST error: ".$HTTP_POST_FILES['userfile']['error'];
    if ((strpos($err_msg, "\n") === 0) {
      $err_lines = explode("\n", $err_msg);
      foreach ($err_lines as $msg) {
        error_log($msg, 0);
      }
    } else {
      error_log($err_msg, 0)
    }
    break;
?>

if files are not getting uploaded and $_FILE array is empty ..and your code looks fine..then check php.ini file..the file_uploads option should be turned 'On' to allow file uploads. Turn it on and restart apache to have effect .

Just a little tip to info at metaltoad's comment:
It's good practice to print error code when it can't be recognized:
  default: //print the error code
   echo "Unrecognized error code: ".$HTTP_POST_FILES['userfile']['error'];
   break;