章 31. 魔术引号

魔术引号(Magic Quote)是一个自动将进入 PHP 脚本的数据进行转义的过程。最好在编码时不要转义而在运行时根据需要而转义。

什么是魔术引号

当打开时,所有的 '(单引号),"(双引号),\(反斜线)和 NULL 字符都会被自动加上一个反斜线进行转义。这和 addslashes() 作用完全相同。

一共有三个魔术引号指令:

  • magic_quotes_gpc

    影响到 HTTP 请求数据(GET,POST 和 COOKIE)。不能在运行时改变。在 PHP 中默认值为 on

    参见 get_magic_quotes_gpc()

  • magic_quotes_runtime

    如果打开的话,大部份从外部来源取得数据并返回的函数,包括从数据库和文本文件,所返回的数据都会被反斜线转义。该选项可在运行的时改变,在 PHP 中的默认值为 off

    参见 set_magic_quotes_runtime()get_magic_quotes_runtime()

  • magic_quotes_sybase

    如果打开的话,将会使用单引号对单引号进行转义而非反斜线。此选项会完全覆盖 magic_quotes_gpc。如果同时打开两个选项的话,单引号将会被转义成 ''。而双引号、反斜线 和 NULL 字符将不会进行转义。

    如何取得其值参见 ini_get()


add a note add a note User Contributed Notes
webmaster at kevinjb dot com
12-Jul-2007 08:12
In response to jfrim at idirect dot com and the poster at 17-Jan-2007 09:37:

Here's the code I use:

<?php
if (get_magic_quotes_gpc()) {
   function
stripslashes_array($array) {
       return
is_array($array) ? array_map('stripslashes_array', $array) : stripslashes($array);
   }

  
$_COOKIE = stripslashes_array($_COOKIE);
  
$_FILES = stripslashes_array($_FILES);
  
$_GET = stripslashes_array($_GET);
  
$_POST = stripslashes_array($_POST);
  
$_REQUEST = stripslashes_array($_REQUEST);
}
?>

Magic_quotes_gpc does NOT effect $_SERVER or $_ENV, I tested this myself on Windows with Apache and PHP 5. Removing slashes from them when there were none added to begin with ruins the variables in them!

I'm not sure at the moment whether it affects $_FILES or not, still looking into that one.
26-Feb-2007 07:57
Or more simply:
<?php   
private function stripslashes_deep($value) {
      
$value = is_array($value) ? array_map(array($this, "stripslashes_deep"), $value) : stripslashes($value);
       return
$value;
   }
?>
17-Jan-2007 05:37
I think most of the people posting below are a little confused about how this works...

To the person who said use addslashes rather than stripslashes... Well, the prefered use of MAGIC_QUOTES_GPC is off, so if you are designing code in such a manner well, using addlashes is of course going to do the same thing as having it turned on. DUH!

Next on the agenda, is the guy who posted the code which the above anonymous person(s) made a comment about. Good, except design your code to not use the HTTP_GET_VARS etc at all, PHP3 is completely outdated... Turn off these options in your .INI/.htaccess/registry files (etc) as well! Additionally, I do not believe that MAGIC_QUOTES affects $_SERVER or $_ENV. I also don't think it affects $_FILES however these values ARE submitted from the user therefor may get escaped.

Heres some code directly from a CMS I'm working on.

# strips slashes to a multi dimensional array, by reference
   function stripslashes_arrays(&$array) {
     if ( is_array($array) ) {
         $keys = array_keys($array);
         foreach ( $keys as $key ) {
           if ( is_array($array[$key]) ) {
               stripslashes_arrays($array[$key]);
           }
           else {
               $array[$key] = stripslashes($array[$key]);
           }
         }
     }
   }
  
# --- Handle input var escapes
# magic_quotes_runtime could corrupt data,
# so make sure it's turned off...
   set_magic_quotes_runtime(0);
# All escapes are handled from code...
# So rather, strip slashes if magic quotes is enabled
   if( get_magic_quotes_gpc() ) {
     stripslashes_arrays($_GET);
     stripslashes_arrays($_POST);
     stripslashes_arrays($_COOKIE);
#      stripslashes_arrays($_FILES);
# verify $_FILES gets escapes by MAGIC_QUOTES first
   }
Thomas dot Hoggard at gmail dot com
10-Nov-2006 09:09
/****
*    Recursivly removes all magicQuotes with multi-dimensional array support
****/
function removeMagicQuotes ($postArray, $trim = false)
{
   if (get_magic_quotes_gpc() == 1)
   {
       $newArray = array();   
      
       foreach ($postArray as $key => $val)
       {
           if (is_array($val))
           {
               $newArray[$key] = removeMagicQuotes ($val, $trim);
           }
           else
           {
               if ($trim == true)
               {
                   $val = trim($val);
               }
               $newArray[$key] = stripslashes($val);
           }
       }   
      
       return $newArray;   
   }
   else
   {
       return $postArray;   
   }       
}
judas dot iscariote at gmail dot com
08-Mar-2006 07:33
Just for the record. this feature has been removed as of PHP6.
now PHP works always like if magic_quotes_gpc Off.

get_magic_quotes_gpc, get_magic_quotes_runtime are kept but always return false, set_magic_quotes_runtime raises an E_CORE_ERROR.

this is great news, magic_quotes were a big annoyance.
27-Feb-2006 11:11
Using the .htaccess file may not always be possible for instance if you are running php on a windows IIS server.

Also the code by jfrim at idirect dot com doesn't actually fix the problem as it is stripping slashes, what you need to do is addslashes to things coming in.

the code by jfrim at idirect dot com is the right idea though although rather than saying stripslashes, you simply need to say addslashes and it should work.
edward at example dot com
07-Feb-2006 12:55
All the code listed on this page is not necessary if you use the php_flag directive in a .htaccess file. This allows you to disable magic quotes completely, without the need to adjust your php.ini file or (re)process the user's input.

Just take a look at http://www.php.net/manual/en/security.magicquotes.php#55935

Gist of his note: in the .htaccess file, add a line

php_flag magic_quotes_gpc off

That's it. Thank you very much, richard dot spindler :) !
jfrim at idirect dot com
27-Jan-2006 06:31
Unfortunately magic_quotes_gpc can not be changed at run-time, but here's a code block which will effectively get rid of it when executed.  Use this for PHP scripts which must be portable or run on servers where magic_quotes_gpc could be configured either way.

Note that the PHP help is a little misleading...  Magic_quotes_gpc affects more than just the Get, Post, and Cookie data!

<?php
//Prevent Magic Quotes from affecting scripts, regardless of server settings

//Make sure when reading file data,
//PHP doesn't "magically" mangle backslashes!
set_magic_quotes_runtime(FALSE);

if (
get_magic_quotes_gpc()) {
  
/*
   All these global variables are slash-encoded by default,
   because    magic_quotes_gpc is set by default!
   (And magic_quotes_gpc affects more than just $_GET, $_POST, and $_COOKIE)
   */
  
$_SERVER = stripslashes_array($_SERVER);
  
$_GET = stripslashes_array($_GET);
  
$_POST = stripslashes_array($_POST);
  
$_COOKIE = stripslashes_array($_COOKIE);
  
$_FILES = stripslashes_array($_FILES);
  
$_ENV = stripslashes_array($_ENV);
  
$_REQUEST = stripslashes_array($_REQUEST);
  
$HTTP_SERVER_VARS = stripslashes_array($HTTP_SERVER_VARS);
  
$HTTP_GET_VARS = stripslashes_array($HTTP_GET_VARS);
  
$HTTP_POST_VARS = stripslashes_array($HTTP_POST_VARS);
  
$HTTP_COOKIE_VARS = stripslashes_array($HTTP_COOKIE_VARS);
  
$HTTP_POST_FILES = stripslashes_array($HTTP_POST_FILES);
  
$HTTP_ENV_VARS = stripslashes_array($HTTP_ENV_VARS);
   if (isset(
$_SESSION)) {    #These are unconfirmed (?)
      
$_SESSION = stripslashes_array($_SESSION, '');
      
$HTTP_SESSION_VARS = stripslashes_array($HTTP_SESSION_VARS, '');
   }
  
/*
   The $GLOBALS array is also slash-encoded, but when all the above are
   changed, $GLOBALS is updated to reflect those changes.  (Therefore
   $GLOBALS should never be modified directly).  $GLOBALS also contains
   infinite recursion, so it's dangerous...
   */
}

function
stripslashes_array($data) {
   if (
is_array($data)){
       foreach (
$data as $key => $value){
          
$data[$key] = stripslashes_array($value);
       }
       return
$data;
   }else{
       return
stripslashes($data);
   }
}
?>
07-Dec-2005 02:09
You should try to avoid magic_quotes in all its flavors, use add_slashes() and strip_slashes() instead with user input and you will save time and avoid common problems that come along.

You should know also that if your server has php suexec enabled you won't be able use php_flag in .htaccess file to change php values like magic_quotes or register_globals. In this case you might wanna try creating a php.ini file on the same directory as your script and add something like this:

magic_quotes_runtime=off
magic_quotes_gpc=off
magic_quotes_sybase=off
register_globals=on ; only as an example

----
Mel
http://www.webhostingjournal.net/
richard dot spindler at gmail dot com
18-Aug-2005 08:59
to turn of magic quotes put the following line into the .htaccess file:

php_flag magic_quotes_gpc off
17-Jul-2005 02:44
Bright minds will have noticed, that one uses stripslashes() once on the input and saves that content for further processing. Then use addslashes() once before sending the content to the database or flat file.

Hint: if the application is using a MySql database, don't use addslashes() but mysql_real_escape_string().
nitrous at fuckoff dot com
26-Jan-2005 07:01
This "feature" is the cause of so many escaping problems.  It's very important to understand the implications of what magic quotes really do.

Nearly every call, except those being written directly to the database, using user submitted data will require a call to strip_slashes.  It gets very ugly very fast.

What should be done is proper escaping of shell parameters and database parameters. PHP provides several escaping functions intended for this purpose. Slashes alone don't cut it anyway.