PHP: POST 方法上传

POST 方法上传

本特性可以使用户上传文本和二进制文件。用 PHP 的认证和文件操作函数，可以完全控制允许哪些人上传以及文件上传后怎样处理。

PHP 能够接受任何来自符合 RFC-1867 标准的浏览器上传的文件。

注意: 相关的设置

请参阅 php.ini 的 file_uploads，upload_max_filesize，upload_tmp_dir，post_max_size 以及 max_input_time 设置选项。

请注意 PHP 也支持 PUT 方法的文件上传，Netscape Composer 和 W3C 的 Amaya 客户端使用这种方法。请参阅对 PUT 方法的支持以获取更多信息。

示例 #1 文件上传表单

可以如下建立一个特殊的表单来支持文件上传：

<!-- The data encoding type, enctype, MUST be specified as below -->
<form enctype="multipart/form-data" action="__URL__" method="POST">
    <!-- MAX_FILE_SIZE must precede the file input field -->
    <input type="hidden" name="MAX_FILE_SIZE" value="30000" />
    <!-- Name of input element determines name in $_FILES array -->
    Send this file: <input name="userfile" type="file" />
    <input type="submit" value="Send File" />
</form>

以上范例中的 __URL__ 应该被换掉，指向一个真实的 PHP 文件。

MAX_FILE_SIZE 隐藏字段（单位为字节）必须放在文件输入字段之前，其值为接收文件的最大尺寸。这是对浏览器的一个建议，PHP 也会检查此项。在浏览器端可以简单绕过此设置，因此不要指望用此特性来阻挡大文件。实际上，PHP 设置中的上传文件最大值是不会失效的。但是最好还是在表单中加上此项目，因为它可以避免用户在花时间等待上传大文件之后才发现文件过大上传失败的麻烦。

注意:
要确保文件上传表单的属性是 enctype="multipart/form-data"，否则文件上传不了。

全局变量 $_FILES 包含有所有上传的文件信息。数组的内容来自以下范例表单。我们假设文件上传字段的名称如下例所示，为 userfile。名称可随意命名。

$_FILES['userfile']['name']: 客户端机器文件的原名称。
$_FILES['userfile']['type']: 文件的 MIME 类型，如果浏览器提供此信息的话。一个例子是“image/gif”。不过此 MIME 类型在 PHP 端并不检查，因此不要想当然认为有这个值。
$_FILES['userfile']['size']: 已上传文件的大小，单位为字节。
$_FILES['userfile']['tmp_name']: 文件被上传后在服务端储存的临时文件名。
$_FILES['userfile']['error']: 和该文件上传相关的错误代码。
$_FILES['userfile']['full_path']: 浏览器提交的完整路径。该值并不总是包含真实的目录结构，因此不能被信任。从 PHP 8.1.0 起可用。

文件被上传后，默认地会被储存到服务端的默认临时目录中，除非 php.ini 中的 upload_tmp_dir 设置为其它的路径。服务端的默认临时目录可以通过更改 PHP 运行环境的环境变量 TMPDIR 来重新设置，但是在 PHP 脚本内部通过运行 putenv() 函数来设置是不起作用的。该环境变量也可以用来确认其它的操作也是在上传的文件上进行的。

示例 #2 验证上传的文件

请查阅函数 is_uploaded_file() 和 move_uploaded_file() 以获取进一步的信息。以下范例处理由表单提供的文件上传。

<?php
$uploaddir = '/var/www/uploads/';
$uploadfile = $uploaddir . basename($_FILES['userfile']['name']);

echo '<pre>';
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) {
    echo "File is valid, and was successfully uploaded.\n";
} else {
    echo "Possible file upload attack!\n";
}

echo 'Here is some more debugging info:';
print_r($_FILES);

print "</pre>";

?>

接受上传文件的 PHP 脚本为了决定接下来要对该文件进行哪些操作，应该实现任何逻辑上必要的检查。例如可以用 $_FILES['userfile']['size'] 变量来排除过大或过小的文件，也可以通过 $_FILES['userfile']['type'] 变量来排除文件类型和某种标准不相符合的文件，但只把这个当作一系列检查中的第一步，因为此值完全由客户端控制而在 PHP 端并不检查。同时，还可以通过 $_FILES['userfile']['error'] 变量来根据不同的错误代码来计划下一步如何处理。不管怎样，要么将该文件从临时目录中删除，要么将其移动到其它的地方。

如果表单中没有选择上传的文件，则 PHP 变量 $_FILES['userfile']['size'] 的值将为 0，$_FILES['userfile']['tmp_name'] 将为空。

如果该文件没有被移动到其它地方也没有被改名，则该文件将在表单请求结束时被删除。

示例 #3 上传一组文件

PHP 的 HTML 数组特性甚至支持文件类型。

<form action="" method="post" enctype="multipart/form-data">
<p>Pictures:
<input type="file" name="pictures[]" />
<input type="file" name="pictures[]" />
<input type="file" name="pictures[]" />
<input type="submit" value="Send" />
</p>
</form>

<?php
foreach ($_FILES["pictures"]["error"] as $key => $error) {
    if ($error == UPLOAD_ERR_OK) {
        $tmp_name = $_FILES["pictures"]["tmp_name"][$key];
        // basename() may prevent filesystem traversal attacks;
        // further validation/sanitation of the filename may be appropriate
        $name = basename($_FILES["pictures"]["name"][$key]);
        move_uploaded_file($tmp_name, "data/$name");
    }
}
?>

File upload progress bar can be implemented using Session Upload Progress.

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User Contributed Notes 12 notes

down

daevid at daevid dot com ¶

15 years ago


I think the way an array of attachments works is kind of cumbersome. Usually the PHP guys are right on the money, but this is just counter-intuitive. It should have been more like:

Array
(
    [0] => Array
        (
            [name] => facepalm.jpg
            [type] => image/jpeg
            [tmp_name] => /tmp/phpn3FmFr
            [error] => 0
            [size] => 15476
        )

    [1] => Array
        (
            [name] => 
            [type] => 
            [tmp_name] => 
            [error] => 4
            [size] => 
        )
)

and not this
Array
(
    [name] => Array
        (
            [0] => facepalm.jpg
            [1] => 
        )

    [type] => Array
        (
            [0] => image/jpeg
            [1] => 
        )

    [tmp_name] => Array
        (
            [0] => /tmp/phpn3FmFr
            [1] => 
        )

    [error] => Array
        (
            [0] => 0
            [1] => 4
        )

    [size] => Array
        (
            [0] => 15476
            [1] => 0
        )
)

Anyways, here is a fuller example than the sparce one in the documentation above:

<?php
foreach ($_FILES["attachment"]["error"] as $key => $error)
{
       $tmp_name = $_FILES["attachment"]["tmp_name"][$key];
       if (!$tmp_name) continue;

       $name = basename($_FILES["attachment"]["name"][$key]);

    if ($error == UPLOAD_ERR_OK)
    {
        if ( move_uploaded_file($tmp_name, "/tmp/".$name) )
            $uploaded_array[] .= "Uploaded file '".$name."'.<br/>\n";
        else
            $errormsg .= "Could not move uploaded file '".$tmp_name."' to '".$name."'<br/>\n";
    }
    else $errormsg .= "Upload error. [".$error."] on file '".$name."'<br/>\n";
}
?>

down

mpyw ¶

8 years ago


Do not use Coreywelch or Daevid's way, because their methods can handle only within two-dimensional structure. $_FILES can consist of any hierarchy, such as 3d or 4d structure.

The following example form breaks their codes:

<form action="" method="post" enctype="multipart/form-data">
    <input type="file" name="files[x][y][z]">
    <input type="submit">
</form>

As the solution, you should use PSR-7 based zendframework/zend-diactoros.

GitHub:

https://github.com/zendframework/zend-diactoros

Example:

<?php

use Psr\Http\Message\UploadedFileInterface;
use Zend\Diactoros\ServerRequestFactory;

$request = ServerRequestFactory::fromGlobals();

if ($request->getMethod() !== 'POST') {
    http_response_code(405);
    exit('Use POST method.');
}

$uploaded_files = $request->getUploadedFiles();

if (
    !isset($uploaded_files['files']['x']['y']['z']) ||
    !$uploaded_files['files']['x']['y']['z'] instanceof UploadedFileInterface
) {
    http_response_code(400);
    exit('Invalid request body.');
}

$file = $uploaded_files['files']['x']['y']['z'];

if ($file->getError() !== UPLOAD_ERR_OK) {
    http_response_code(400);
    exit('File uploading failed.');
}

$file->moveTo('/path/to/new/file');

?>

down

coreywelch+phpnet at gmail dot com ¶

8 years ago

down

anon ¶

9 years ago


For clarity; the reason you would NOT want to replace the example script with
$uploaddir = './';
is because if you have no coded file constraints a nerd could upload a php script with the same name of one of your scripts in the scripts directory.

Given the right settings and permissions php-cgi is capable of replacing even php files.

Imagine if it replaced the upload post processor file itself. The next "upload" could lead to some easy exploits.

Even when replacements are not possible; uploading an .htaccess file could cause some problems, especially if it is sent after the nerd throws in a devious script to use htaccess to redirect to his upload.

There are probably more ways of exploiting it. Don't let the nerds get you.

More sensible to use a fresh directory for uploads with some form of unique naming algorithm; maybe even a cron job for sanitizing the directory so older files do not linger for too long.

down

fravadona at gmail dot com ¶

4 years ago


mpyw is right, PSR-7 is awesome but a little overkill for simple projects (in my opinion).

Here's an example of function that returns the file upload metadata in a (PSR-7 *like*) normalized tree. This function deals with whatever dimension of upload metadata.

I kept the code extremely simple, it doesn't validate anything in $_FILES, etc... AND MOST IMPORTANTLY, it calls array_walk_recursive in an *undefined behaviour* way!!!

You can test it against the examples of the PSR-7 spec ( https://www.php-fig.org/psr/psr-7/#16-uploaded-files ) and try to add your own checks that will detect the error in the last example ^^

<?php
/**
 *  THIS CODE IS ABSOLUTELY NOT MEANT FOR PRODUCTION !!! MAY ITS INSIGHTS HELP YOU !!!
 */
function getNormalizedFiles()
{
  $normalized = array();

  if ( isset($_FILES) ) { 
    
    foreach ( $_FILES as $field => $metadata ) {
      
      $normalized[$field] = array(); // needs initialization for array_replace_recursive
      
      foreach ( $metadata as $meta => $data ) { // $meta is 'tmp_name', 'error', etc...
        
        if ( is_array($data) ) {
          
          // insert the current meta just before each leaf !!! WRONG USE OF ARRAY_WALK_RECURSIVE !!!
          array_walk_recursive($data, function (&$v,$k) use ($meta) { $v = array( $meta => $v ); });
          
          // fuse the current metadata with the previous ones
          $normalized[$field] = array_replace_recursive($normalized[$field], $data);
        
        } else {
          $normalized[$field][$meta] = $data;
        }
      } 
    }
  } 
  return $normalized;
}
?>

down

eslindsey at gmail dot com ¶

15 years ago


Also note that since MAX_FILE_SIZE hidden field is supplied by the browser doing the submitting, it is easily overridden from the clients' side.  You should always perform your own examination and error checking of the file after it reaches you, instead of relying on information submitted by the client.  This includes checks for file size (always check the length of the actual data versus the reported file size) as well as file type (the MIME type submitted by the browser can be inaccurate at best, and intentionally set to an incorrect value at worst).

down

Mark ¶

14 years ago


$_FILES will be empty if a user attempts to upload a file greater than post_max_size in your php.ini

post_max_size should be >= upload_max_filesize in your php.ini.

down

claude dot pache at gmail dot com ¶

15 years ago


Note that the MAX_FILE_SIZE hidden field is only used by the PHP script which receives the request, as an instruction to reject files larger than the given bound. This field has no significance for the browser, it does not provide a client-side check of the file-size, and it has nothing to do with web standards or browser features.

down

-2

Anonymous ¶

7 years ago


I have found it useful to re-order the multidimensional $_FILES array into a more intuitive format, as proposed by many other developers already. 

Unfortunately, most of the proposed functions are not able to re-order the $_FILES array when it has more than 1 additional dimension.

Therefore, I would like to contribute the function below, which is capable of meeting the aforementioned requirement:

<?php
    function get_fixed_files() {
        $function = function($files, $fixed_files = array(), $path = array()) use (&$function) {
            foreach ($files as $key => $value) {
                $temp = $path;
                $temp[] = $key;
            
                if (is_array($value)) {
                    $fixed_files = $function($value, $fixed_files, $temp);
                } else {
                    $next = array_splice($temp, 1, 1);
                    $temp = array_merge($temp, $next);
                    
                    $new = &$fixed_files;
                    
                    foreach ($temp as $key) {
                        $new = &$new[$key];
                    }
                    
                    $new = $value;
                }
            }
            
            return $fixed_files;
        };
        
        return $function($_FILES);
    }
?>

Side note: the unnamed function within the function is used to avoid confusion regarding the arguments necessary for the recursion within the function, for example when viewing the function in an IDE.

down

-5

Age Bosma ¶

13 years ago


"If no file is selected for upload in your form, PHP will return $_FILES['userfile']['size'] as 0, and $_FILES['userfile']['tmp_name'] as none."

Note that the situation above is the same when a file exceeding the MAX_FILE_SIZE hidden field is being uploaded. In this case $_FILES['userfile']['size'] is also set to 0, and $_FILES['userfile']['tmp_name'] is also empty. The difference would only be the error code.
Simply checking for these two conditions and assuming no file upload has been attempted is incorrect.

Instead, check if $_FILES['userfile']['name'] is set or not. If it is, a file upload has at least been attempted (a failed attempt or not). If it is not set, no attempt has been made.

down

-14

bimal at sanjaal dot com ¶

9 years ago


Some suggestions here:

1. It is always better to check for your error status. If MAX_FILE_SIZE is active and the uploaded file crossed the limit, it will set the error. So, only when error is zero (0), move the file.

2. If possible, never allow your script to upload in the path where file can be downloaded. Point your upload path to outside of public_html area or prevent direct browsing (using .htaccess restrictions). Think, if someone uploads malicious code, specially php codes, they will be executed on the server.

3. Do not use the file name sent by the client. Regenerate a new name for newly uploaded file. This prevents overwriting your old files.

4. Regularly track the disk space consumed, if you are running out of storage.

down

-18

katrinaelaine6 at gmail dot com ¶

7 years ago


Here's a complete example of the $_FILES array with nested and non-nested names. Let's say we have this html form:

<form action="test.php" method="post">

    <input type="file" name="single" id="single">

    <input type="file" name="nested[]"          id="nested_one">
    <input type="file" name="nested[root]"      id="nested_root">         
    <input type="file" name="nested[][]"        id="nested_two"> 
    <input type="file" name="nested[][parent]"  id="nested_parent">
    <input type="file" name="nested[][][]"      id="nested_three">
    <input type="file" name="nested[][][child]" id="nested_child">

    <input type="submit" value="Submit">

</form>

In the test.php file:

<?php

    print_r($_FILES);
    exit;

?>

If we upload a text file with the same name as the input id for each input and click submit, test.php will output this:

<?php

Array
(

    [single] => Array
        (
            [name] => single.txt
            [type] => text/plain
            [tmp_name] => /tmp/phpApO28i
            [error] => 0
            [size] => 3441
        )

    [nested] => Array
        (
            [name] => Array
                (
                    [0] => nested_one.txt
                    [root] => nested_root.txt
                    [1] => Array
                        (
                            [0] => nested_two.txt
                        )

                    [2] => Array
                        (
                            [parent] => nested_parent.txt
                        )

                    [3] => Array
                        (
                            [0] => Array
                                (
                                    [0] => nested_three.txt
                                )

                        )

                    [4] => Array
                        (
                            [0] => Array
                                (
                                    [child] => nested_child.txt
                                )

                        )

                )

            // type, tmp_name, size, and error will have the same structure.
        )

)

?>

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