Magic Quotes in PHP


Why use Magic Quotes

  • Useful for beginners Magic quotes are implemented in PHP to help code written by beginners from being dangerous. Although SQL Injection is still possible with magic quotes on, the risk is reduced.
  • Convenience For inserting data into a database, magic quotes essentially runs addslashes() on all Get, Post, and Cookie data, and does so automagically.

Why not to use Magic Quotes

  • Portability Assuming it to be on, or off, affects portability. Use get_magic_quotes_gpc() to check for this, and code accordingly.
  • Performance Because not every piece of escaped data is inserted into a database, there is a performance loss for escaping all this data. Simply calling on the escaping functions (like addslashes()) at runtime is more efficient. Although php.ini-dist enables these directives by default, php.ini-recommended disables it. This recommendation is mainly due to performance reasons.
  • Inconvenience Because not all data needs escaping, it’s often annoying to see escaped data where it shouldn’t be. For example, emailing from a form, and seeing a bunch of \’ within the email. To fix, this may require excessive use of stripslashes().

Disabling Magic Quotes

The magic_quotes_gpc directive may only be disabled at the system level, and not at runtime. In otherwords, use of ini_set() is not an option.

Example #1 Disabling magic quotes server side

An example that sets the value of these directives to Off in php.ini. For additional details, read the manual section titled How to change configuration settings.

; Magic quotes
;

; Magic quotes for incoming GET/POST/Cookie data.
magic_quotes_gpc = Off

; Magic quotes for runtime-generated data, e.g. data from SQL, from exec(), etc.
magic_quotes_runtime = Off

; Use Sybase-style magic quotes (escape ' with '' instead of \').
magic_quotes_sybase = Off

If access to the server configuration is unavailable, use of .htaccess is also an option. For example:

php_flag magic_quotes_gpc Off

In the interest of writing portable code (code that works in any environment), like if setting at the server level is not possible, here’s an example to disable magic_quotes_gpc at runtime. This method is inefficient so it’s preferred to instead set the appropriate directives elsewhere.

Example #2 Disabling magic quotes at runtime

<?php
if (get_magic_quotes_gpc()) {
function stripslashes_deep($value)
{
$value = is_array($value) ?
array_map('stripslashes_deep', $value) :
stripslashes($value);

return $value;
}

$_POST = array_map(‘stripslashes_deep’, $_POST);
$_GET = array_map(‘stripslashes_deep’, $_GET);
$_COOKIE = array_map(‘stripslashes_deep’, $_COOKIE);
$_REQUEST = array_map(‘stripslashes_deep’, $_REQUEST);
}
?>

What are Magic Quotes

When on, all (single-quote), (double quote), \ (backslash) and NULL characters are escaped with a backslash automatically. This is identical to what addslashes() does.

There are three magic quote directives:

  • magic_quotes_gpc Affects HTTP Request data (GET, POST, and COOKIE). Cannot be set at runtime, and defaults to on in PHP. See also get_magic_quotes_gpc().
  • magic_quotes_runtime If enabled, most functions that return data from an external source, including databases and text files, will have quotes escaped with a backslash. Can be set at runtime, and defaults to off in PHP. See also set_magic_quotes_runtime() and get_magic_quotes_runtime().
  • magic_quotes_sybase If enabled, a single-quote is escaped with a single-quote instead of a backslash. If on, it completely overrides magic_quotes_gpc. Having both directives enabled means only single quotes are escaped as . Double quotes, backslashes and NULL’s will remain untouched and unescaped. See also ini_get() for retrieving its value.

get_magic_quotes_gpc()

(PHP 4, PHP 5)

get_magic_quotes_gpc — Gets the current configuration setting of magic quotes gpc

Description

int get_magic_quotes_gpc ( void )

Returns the current configuration setting of magic_quotes_gpc

Keep in mind that the setting magic_quotes_gpc will not work at runtime.

For more information about magic_quotes, see this security section.

Return Values

Returns 0 if magic quotes gpc are off, 1 otherwise.

Examples

Example #1 get_magic_quotes_gpc() example

<?php
echo get_magic_quotes_gpc();        // 1
echo $_POST['lastname'];            // O\'reilly
echo addslashes($_POST['lastname']); // O\\'reilly
if (!get_magic_quotes_gpc()) {
$lastname = addslashes($_POST[‘lastname’]);
} else {
$lastname = $_POST[‘lastname’];
}

echo $lastname; // O\’reilly
$sql = “INSERT INTO lastnames (lastname) VALUES (‘$lastname’)”;
?>

Notes

Note: If the directive magic_quotes_sybase is ON it will completely override magic_quotes_gpc. So even when get_magic_quotes_gpc() returns TRUE neither double quotes, backslashes or NUL’s will be escaped. Only single quotes will be escaped. In this case they’ll look like:

get_magic_quotes_runtime

(PHP 4, PHP 5)

get_magic_quotes_runtime — Gets the current active configuration setting of magic_quotes_runtime

Description

int get_magic_quotes_runtime ( void )

Returns the current active configuration setting of magic_quotes_runtime.

Return Values

Returns 0 if magic quotes runtime is off, 1 otherwise.

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