downloads | documentation | faq | getting help | mailing lists | licenses | wiki | reporting bugs | php.net sites | links | conferences | my php.net

search for in the

mysql_result> <mysql_query
Last updated: Fri, 24 Jul 2009

view this page in

mysql_real_escape_string

(PHP 4 >= 4.3.0, PHP 5)

mysql_real_escape_string — mysql_query에서 특수 문자열을 이스케이프하기위해 사용

설명

string mysql_real_escape_string ( string $unescaped_string [, resource $link_identifier ] )

unescaped_string 된 문자열에서 접속의 현재 문자 집합으로 특수 문자열을 이스케이프하여 mysql_query() 수행시 안전하게 질의할 수 있도록 한다. 이진 데이터를 입력할 경우 이 함수를 사용해야 한다.

mysql_real_escape_string()는 MySQL 라이브러리 함수인 mysql_real_escape_string를 호출하여, 다음의 문자에 백슬래시를 붙인다: \x00, \n, \r, \, ', ", \x1a.

이 함수는 MySQL로 질의를 전송하기 전에 안전하게 데이터를 만들기 위해 항상 사용해야한다.

인수

unescaped_string

이스케이프할 문자열.

link_identifier

MySQL 연결. 지정하지 않으면 mysql_connect()로 연 마지막 연결을 사용합니다. 연결이 없으면, 인수 없이 mysql_connect()를 호출하여 연결을 만듭니다. 연결이 성립되지 않으면 E_WARNING 등급의 오류를 생성합니다.

반환값

이스케이프된 문자열을 반환하고 에러가 발생하면 FALSE를 반환한다.

예제

Example #1 mysql_real_escape_string() 예제

<?php
// Connect
$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password')
    OR die(mysql_error());

// Query
$query = sprintf("SELECT * FROM users WHERE user='%s' AND password='%s'",
            mysql_real_escape_string($user),
            mysql_real_escape_string($password));
?>

Example #2 SQL 인젝션 공격(Injection Attack)의 예

<?php
// Query database to check if there are any matching users
$query = "SELECT * FROM users WHERE user='{$_POST['username']}' AND password='{$_POST['password']}'";
mysql_query($query);

// We didn't check $_POST['password'], it could be anything the user wanted! For example:
$_POST['username'] = 'aidan';
$_POST['password'] = "' OR ''='";

// This means the query sent to MySQL would be:
echo $query;
?>

MySQL로 전송되는 질의: 

SELECT * FROM users WHERE user='aidan' AND password='' OR ''=''

유효한 비밀번호 없이 누구나 접속하여 접근이 가능하다.

Example #3 "Best Practice" 질의

mysql_real_escape_string()은 각 변수에 대해 SQL 인젝션을 방지한다. 이 예제는 Magic Quotes 설정과는 별개로 데이터베이스를 질의하는 "best practice" 방법을 시연한다.

<?php
if (isset($_POST['product_name']) && isset($_POST['product_description']) && isset($_POST['user_id'])) {
    // 접속
    $link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password');

    if(!is_resource($link)) {

        echo "서버 접속 실패\n";
        // ... 오류를 적절히 기록

    } else {

        // ON일 경우 magic_quotes_gpc/magic_quotes_sybase 효과 제거

        if(get_magic_quotes_gpc()) {
            $product_name        = stripslashes($_POST['product_name']);
            $product_description = stripslashes($_POST['product_description']);
        } else {
            $product_name        = $_POST['product_name'];
            $product_description = $_POST['product_description'];
        }

        // 안전한 질의 만들기
        $query = sprintf("INSERT INTO products (`name`, `description`, `user_id`) VALUES ('%s', '%s', %d)",
                    mysql_real_escape_string($product_name, $link),
                    mysql_real_escape_string($product_description, $link),
                    $_POST['user_id']);

        mysql_query($query, $link);

        if (mysql_affected_rows($link) > 0) {
            echo "Product inserted\n";
        }
    }
} else {
    echo "Fill the form property\n";
}
?>

SQL 인젝션 공격이 동작하지 않으며 질의가 정확하게 실행될 것이다.

주의

Note: mysql_real_escape_string()을 사용하기 전에 MySQL 접속이 필요하다. 그렇지 않으면 E_WARNING 등급의 에러가 발생되며, FALSE가 반환될 것이다. 만약 link_identifier 가 정의되지 않으면, 최근 MySQL 접속이 사용된다.

Note: magic_quotes_gpc이 활성화되면, stripslashes()가 모든 데이터에 먼저 적용된다. 이 함수를 데이터에 사용하면 이스케이프된 데이터에 중복 처리될 것이다.

Note: 이 함수가 데이터 이스케이프를 위해 사용되지 않으면, 질의는 SQL Injection Attacks으로 취약점이 생기게 된다.

Note: mysql_real_escape_string()는 %와 _를 이스케이프하지는 않는다. LIKE, GRANT, REVOKE와 결합되어 사용되는 와일드카드이기 때문이다.

참고



mysql_result> <mysql_query
Last updated: Fri, 24 Jul 2009
 
add a note add a note User Contributed Notes
mysql_real_escape_string
alan_a_williams [at] hotmail [dot] com
19-Aug-2009 11:17
Just a little something I like to use....

$_GET = array_map('trim', $_GET);
$_POST = array_map('trim', $_POST);
$_COOKIE = array_map('trim', $_COOKIE);
$_REQUEST = array_map('trim', $_REQUEST);
if(get_magic_quotes_gpc()):
    $_GET = array_map('stripslashes', $_GET);
    $_POST = array_map('stripslashes', $_POST);
    $_COOKIE = array_map('stripslashes', $_COOKIE);
    $_REQUEST = array_map('stripslashes', $_REQUEST);
endif;
$_GET = array_map('mysql_real_escape_string', $_GET);
$_POST = array_map('mysql_real_escape_string', $_POST);
$_COOKIE = array_map('mysql_real_escape_string', $_COOKIE);
$_REQUEST = array_map('mysql_real_escape_string', $_REQUEST);

Seems to do the trick ALOT of the time, but I'm going to be honest, it can be a [EDITED] sometimes >_>
Anonymous
02-Aug-2009 10:45
I use the following code in my database connection include file (which is of course called at the start of every page that needs to do some SQL)...
Therefore, all POST and GET vars are automatically escaped before being used anywhere in SQL statements.

<?php
  //This stops SQL Injection in POST vars
  foreach ($_POST as $key => $value) {
    $_POST[$key] = mysql_real_escape_string($value);
  }

  //This stops SQL Injection in GET vars
  foreach ($_GET as $key => $value) {
    $_GET[$key] = mysql_real_escape_string($value);
  }
?>
plgs at ozemail dot com dot au
27-Jul-2009 08:05
Don't forget that if you're using Mysqli (ie, the "improved" Mysql extension) then you need to use the corresponding mysqli function mysqli_real_escape_string().  The parameter order is also different.
Anonymous
13-Jul-2009 03:30
It is because you swapped $key and $item:

Just change this:
<?php
  function mysql_safe ( $item, $key, $type )
  ?>

To:

<?php
        function mysql_safe ( $key, $item, $type )
?>

And it will work as expected.
isaacs dot brian dot c at gmail dot com
12-Jul-2009 06:06
I had wanted to see the merits of dynamically and "automatically" applying mysql_real_escape_string() to $_GET and $_POST as arrays rather than manually each time I would type up a query. I used array_walk_recursive() to call my function "mysql_safe" to apply mysql_real_escape_string() to each key of the $_GET and $_POST arrays.

My function is part of a class, and it is called each time I connect to the database to perform a query:

<?php
class MyClass {
        function mysql_safe ( $key, $item, $type )
        {
            switch( $type )
            {           
                case 'get':
                    if( count( $_GET ) > 0 )
                    {
                        $_GET[$item] = mysql_real_escape_string( $key );
                    }
                break;
                case 'post':
                    if( count( $_POST ) > 0 )
                    {
                        $_POST[$item] = mysql_real_escape_string( $key );
                    }
                break;
            }
        }
       
        function safe_get ( )
        {
            #Flag to only run function once           
            if( $this->get_flag == true ) { return true; }

            array_walk_recursive( $_GET, array( $this, 'mysql_safe' ), 'get' );
            array_walk_recursive( $_POST, array( $this, 'mysql_safe' ), 'post' );
           
            $this->get_flag = true;
        }
}
?>

However, after using this function, I find that it does indeed work, it also creates new $_GET and $_POST values in which $item and $key are swapped. So I end up with $_GET[$item] = $key, as well as $_GET[$key] = $item. I have not yet determined if this is due to the actual coding itself, or my particular method of implementation.

[EDIT BY danbrown AT php DOT net: Contains a bugfix by "Anonymous" on 13-JUL-09 to reorder the user function parameters.]
info at saturnprods dot com
13-Jun-2009 07:37
I always use this function so I don't have to retype over and over the mysql_real_escape_string function.

<?php
function safe($value){
   return mysql_real_escape_string($value);
}
?>

Then, when I am using my code, I simply use:

<?php
$name = safe($_POST["name"]);
$password = safe($_POST["password"]);
?>
kendsnyder at gmail dot com
25-Mar-2009 09:07
<?php

// Here is a simple named binding function for queries that makes SQL more readable:
// $sql = "SELECT * FROM users WHERE user = :user AND password = :password";
// mysql_bind($sql, array('user' => $user, 'password' => $password));
// mysql_query($sql);

function mysql_bind(&$sql, $vals) {
    foreach ($vals as $name => $val) {
        $sql = str_replace(":$name", "'" . mysql_real_escape_string($val) . "'", $sql);
    }
}

?>
Bastiaan Welmers
24-Mar-2008 07:46
This function won't help you when inserting binary data, to me it will get mallformed into the database. Probably UTF-8 combinations will be translated by this function or somewhere else when inserting data when running mysql in UTF-8 mode.

A better way to insert binary data is to transfer it to hexadecimal notation like this example:

<?php
$string = $_REQUEST['string'];
$binary = file_get_contents($_FILE['file']['tmp_name']);

$string = mysql_real_escape_string($string);
$binary_hex = bin2hex($binary);

$query = "INSERT INTO `table` (`key`, `string`, `binary`, `other`) VALUES (NULL, '$string', 0x$binary_hex, '$other')";

?>
Anonymous
03-Mar-2008 06:57
My escape function:

Automatically adds quotes (unless $quotes is false), but only for strings. Null values are converted to mysql keyword "null", booleans are converted to 1 or 0, and numbers are left alone. Also can escape a single variable or recursively escape an array of unlimited depth.

<?php
function db_escape($values, $quotes = true) {
    if (is_array($values)) {
        foreach ($values as $key => $value) {
            $values[$key] = db_escape($value, $quotes);
        }
    }
    else if ($values === null) {
        $values = 'NULL';
    }
    else if (is_bool($values)) {
        $values = $values ? 1 : 0;
    }
    else if (!is_numeric($values)) {
        $values = mysql_real_escape_string($values);
        if ($quotes) {
            $values = '"' . $values . '"';
        }
    }
    return $values;
}
?>
matthijs at yourmediafactory dot com
27-Dec-2007 09:49
In response to Michael D - DigitalGemstones.com:

Check the example again: sprintf(%d) already does the int conversion for you, so it's both perfectly save as well as more elegant than manually casting.
user at NOSPAM dot example dot com
28-Aug-2007 12:16
if you're doing a mysql wildcard query with
LIKE, GRANT, or REVOKE
you may use addcslashes to escape the string:

<?php
$param = mysql_real_escape_string($param);
$param = addcslashes($param, '%_');
?>
brian dot folts at gmail dot com
06-Sep-2006 04:25
mysql_real_escape_string is a bit annoying when you need to do it over an array.

<?php
function mysql_real_escape_array($t){
    return array_map("mysql_real_escape_string",$t);
}
?>

this one just mysql_real_escape's the whole array.

ex) <?php $_POST=mysql_real_escape_array($_POST); ?>

and then you dont have to worry about forgetting to do this.
kael dot shipman at DONTSPAMIT! dot gmail dot com
18-Jul-2006 08:19
It seems to me that you could avoid many hassels by loading valid database values into an array at the beginning of the script, then instead of using user input to query the database directly, use it to query the array you've created. For example:

<?php
//you still have to query safely, so always use cleanup functions like eric256's
$categories = sql_query("select catName from categories where pageID = ?",$_GET['pageID']);
while ($cts = @mysql_fetch_row($categories)) {
 //making $cts both the name and the value of the array variable makes it easier to check for in the future.
 //obviously, this naming system wouldn't work for a multidimensional array
 $cat_ar[$cts[0]] = $cts[0];
}
...

//user selects sorting criteria
//this would be from a query string like '?cats[]=cha&cats[]=fah&cats[]=lah&cats[]=badValue...', etc.
$cats = $_GET['cats'];

//verify that values exist in database before building sorting query
foreach($cats as $c) {
 if ($cat_ar[$c]) { //instead of in_array(); maybe I'm just lazy... (see above note)
  $cats1[] = "'".mysql_real_escape_string($c)."'";
 }
}
$cats = $cats1;
//$cats now contains the filtered and escaped values of the query string

$cat_query = '&& (category_name = \''.implode(' || category_name = \'',$cats).'\')';
//build a sql query insert
//$cat_query is now "&& (category_name = 'cha' || category_name = 'fah' || category_name = 'lah')" - badValue has been removed
//since all values have already been verified and escaped, you can simply use them in a query
//however, since $pageID hasn't been cleaned for this query, you still have to use your cleaning function
$items = sql_query("SELECT * FROM items i, categories c WHERE i.catID = c.catID && pageID = ? $cat_query", $pageID);
nicolas
30-May-2006 08:38
Note that mysql_real_escape_string doesn't prepend backslashes to \x00, \n, \r, and and \x1a as mentionned in the documentation, but actually replaces the character with a MySQL acceptable representation for queries (e.g. \n is replaced with the '\n' litteral). (\, ', and " are escaped as documented) This doesn't change how you should use this function, but I think it's good to know.
add a note add a note

mysql_result> <mysql_query
Last updated: Fri, 24 Jul 2009
 
 
show source | credits | sitemap | contact | advertising | mirror sites