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According to the PHP manual, in order to make code more portable, they recommend using something like the following for escaping data:

if (!get_magic_quotes_gpc()) {
    $lastname = addslashes($_POST['lastname']);
} else {
    $lastname = $_POST['lastname'];
}

I have other validation checks that I will be performing, but how secure is the above strictly in terms of escaping data? I also saw that magic quotes will be deprecated in PHP 6. How will that affect the above code? I would prefer not to have to rely on a database-specific escaping function like mysql_real_escape_string().

 Answers

3

Magic quotes are inherently broken. They were meant to sanitize input to the PHP script, but without knowing how that input will be used it's impossible to sanitize correctly. If anything, you're better off checking if magic quotes are enabled, then calling stripslashes() on $_GET/$_POST/$_COOKIES/$_REQUEST, and then sanitizing your variables at the point where you're using it somewhere. E.g. urlencode() if you're using it in a URL, htmlentities() if you're printing it back to a web page, or using your database driver's escaping function if you're storing it to a database. Note those input arrays could contain sub-arrays so you might need to write a function can recurse into the sub-arrays to strip those slashes too.

The PHP man page on magic quotes agrees:

"This feature has been DEPRECATED as of PHP 5.3.0 and REMOVED as of PHP 5.4.0. Relying on this feature is highly discouraged. Magic Quotes is a process that automagically escapes incoming data to the PHP script. It's preferred to code with magic quotes off and to instead escape the data at runtime, as needed."

Tuesday, August 16, 2022
1

If magic_quotes_runtime is enabled, most functions that return data from any sort of external source including databases and text files will have quotes escaped with a backslash. If magic_quotes_sybase is also on, a single-quote is escaped with a single-quote instead of a backslash.

http://www.php.net/manual/en/info.configuration.php#ini.magic-quotes-runtime

Friday, October 28, 2022
 
mitch
 
1

I think this is a little cleaner and avoids reference bugs:

function unMagicQuotify($ar) {
  $fixed = array();
  foreach ($ar as $key=>$val) {
    if (is_array($val)) {
      $fixed[stripslashes($key)] = unMagicQuotify($val);
    } else {
      $fixed[stripslashes($key)] = stripslashes($val);
    }
  }
  return $fixed;
}

$process = array($_GET,$_POST,$_COOKIE,$_REQUEST);
$fixed = array();
foreach ($process as $index=>$glob) {
  $fixed[$index] = unMagicQuotify($glob);
}
list($_GET,$_POST,$_COOKIE,$_REQUEST) = $fixed;
Wednesday, November 16, 2022
3

As per the manual you can often install a custom php.ini on shared hosting, where mod_php isn't used and the php_value directive thus leads to an error. For suexec/FastCGI setups it is quite common to have a per-webspace php.ini in any case.

--

I don't think O (uppercase letter o) is a valid value to set an ini flag. You need to use a true/false, 1/0, or "on"/"off" value.

ini_set( 'magic_quotes_gpc', 0 );   // doesn't work

EDIT

After checking the list of ini settings, I see that magic_quotes_gpc is a PHP_INI_PERDIR setting (after 4.2.3), which means you can't change it with ini_set() (only PHP_INI_ALL settings can be changed with ini_set())

What this means is you have to use an .htaccess file to do this - OR - implement a script to reverse the effects of magic quotes. Something like this

if ( in_array( strtolower( ini_get( 'magic_quotes_gpc' ) ), array( '1', 'on' ) ) )
{
    $_POST = array_map( 'stripslashes', $_POST );
    $_GET = array_map( 'stripslashes', $_GET );
    $_COOKIE = array_map( 'stripslashes', $_COOKIE );
}
Wednesday, October 19, 2022
5

Only magic_quoted_runtime can be disabled at runtime. But magic_quotes_gpc can’t be disabled at runtime (PHP_INI_ALL changable until PHP 4.2.3, since then PHP_INI_PERDIR); you can only remove them:

if (get_magic_quotes_gpc()) {
    $process = array(&$_GET, &$_POST, &$_COOKIE, &$_REQUEST);
    while (list($key, $val) = each($process)) {
        foreach ($val as $k => $v) {
            unset($process[$key][$k]);
            if (is_array($v)) {
                $process[$key][stripslashes($k)] = $v;
                $process[] = &$process[$key][stripslashes($k)];
            } else {
                $process[$key][stripslashes($k)] = stripslashes($v);
            }
        }
    }
    unset($process);
}

For further information see Disabling Magic Quotes.

Wednesday, November 9, 2022
 
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