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mysqli::real_escape_string

mysqli_real_escape_string

(PHP 5, PHP 7, PHP 8)

mysqli::real_escape_string -- mysqli_real_escape_stringProtège les caractères spéciaux d'une chaîne pour l'utiliser dans une requête SQL, en prenant en compte le jeu de caractères courant de la connexion

Description

Style orienté objet

public mysqli::real_escape_string(string $string): string

Style procédural

mysqli_real_escape_string(mysqli $mysql, string $string): string

Cette fonction est utilisée pour créer une chaîne SQL valide qui pourra être utilisée dans une requête SQL. La chaîne de caractères string est encodée pour produire une chaîne SQL échappée, en tenant compte du jeu de caractères courant de la connexion.

Attention

Sécurité : Le jeu de caractères par défaut

Le jeu de caractères doit être défini soit au niveau serveur, soit avec la fonction API mysqli_set_charset() pour qu'il affecte la fonction mysqli_real_escape_string(). Voir la section sur les concepts on des jeux de caractères pour plus d'informations.

Liste de paramètres

mysql

Seulement en style procédural : Un objet mysqli retourné par la fonction mysqli_connect() ou par la fonction mysqli_init()

string

La chaîne de caractères à échapper.

Les caractères encodés sont NUL (ASCII 0), \n, \r, \, ', ", and Control-Z.

Valeurs de retour

Retourne une chaîne de caractères échappée.

Exemples

Exemple #1 Exemple avec mysqli::real_escape_string()

Style orienté objet

<?php

mysqli_report
(MYSQLI_REPORT_ERROR MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("localhost""my_user""my_password""world");

$city "'s-Hertogenbosch";

/* this query with escaped $city will work */
$query sprintf("SELECT CountryCode FROM City WHERE name='%s'",
    
$mysqli->real_escape_string($city));
$result $mysqli->query($query);
printf("Select returned %d rows.\n"$result->num_rows);

/* this query will fail, because we didn't escape $city */
$query sprintf("SELECT CountryCode FROM City WHERE name='%s'"$city);
$result $mysqli->query($query);

Style procédural

<?php

mysqli_report
(MYSQLI_REPORT_ERROR MYSQLI_REPORT_STRICT);
$mysqli mysqli_connect("localhost""my_user""my_password""world");

$city "'s-Hertogenbosch";

/* this query with escaped $city will work */
$query sprintf("SELECT CountryCode FROM City WHERE name='%s'",
    
mysqli_real_escape_string($mysqli$city));
$result mysqli_query($mysqli$query);
printf("Select returned %d rows.\n"mysqli_num_rows($result));

/* this query will fail, because we didn't escape $city */
$query sprintf("SELECT CountryCode FROM City WHERE name='%s'"$city);
$result mysqli_query($mysqli$query);

Les exemples ci-dessus vont afficher quelque chose de similaire à :

Select returned 1 rows.

Fatal error: Uncaught mysqli_sql_exception: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 's-Hertogenbosch'' at line 1 in...

Voir aussi

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User Contributed Notes 9 notes

up
126
tobias_demuth at web dot de
15 years ago
Note, that if no connection is open, mysqli_real_escape_string() will return an empty string!
up
54
Josef Toman
11 years ago
For percent sign and underscore I use this:
<?php
$more_escaped
= addcslashes($escaped, '%_');
?>
up
42
dave at mausner.us
10 years ago
You can avoid all character escaping issues (on the PHP side) if you use prepare() and bind_param(), as an alternative to placing arbitrary string values in SQL statements.  This works because bound parameter values are NOT passed via the SQL statement syntax.
up
17
therselman at gmail dot com
4 years ago
Presenting several UTF-8 / Multibyte-aware escape functions.

These functions represent alternatives to mysqli::real_escape_string, as long as your DB connection and Multibyte extension are using the same character set (UTF-8), they will produce the same results by escaping the same characters as mysqli::real_escape_string.

This is based on research I did for my SQL Query Builder class:
https://github.com/twister-php/sql

<?php
/**
* Returns a string with backslashes before characters that need to be escaped.
* As required by MySQL and suitable for multi-byte character sets
* Characters encoded are NUL (ASCII 0), \n, \r, \, ', ", and ctrl-Z.
*
* @param string $string String to add slashes to
* @return $string with `\` prepended to reserved characters
*
* @author Trevor Herselman
*/
if (function_exists('mb_ereg_replace'))
{
    function
mb_escape(string $string)
    {
        return
mb_ereg_replace('[\x00\x0A\x0D\x1A\x22\x27\x5C]', '\\\0', $string);
    }
} else {
    function
mb_escape(string $string)
    {
        return
preg_replace('~[\x00\x0A\x0D\x1A\x22\x27\x5C]~u', '\\\$0', $string);
    }
}

?>

Characters escaped are (the same as mysqli::real_escape_string):

00 = \0 (NUL)
0A = \n
0D = \r
1A = ctl-Z
22 = "
27 = '
5C = \

Note: preg_replace() is in PCRE_UTF8 (UTF-8) mode (`u`).

Enhanced version:

When escaping strings for `LIKE` syntax, remember that you also need to escape the special characters _ and %

So this is a more fail-safe version (even when compared to mysqli::real_escape_string, because % characters in user input can cause unexpected results and even security violations via SQL injection in LIKE statements):

<?php

/**
* Returns a string with backslashes before characters that need to be escaped.
* As required by MySQL and suitable for multi-byte character sets
* Characters encoded are NUL (ASCII 0), \n, \r, \, ', ", and ctrl-Z.
* In addition, the special control characters % and _ are also escaped,
* suitable for all statements, but especially suitable for `LIKE`.
*
* @param string $string String to add slashes to
* @return $string with `\` prepended to reserved characters
*
* @author Trevor Herselman
*/
if (function_exists('mb_ereg_replace'))
{
    function
mb_escape(string $string)
    {
        return
mb_ereg_replace('[\x00\x0A\x0D\x1A\x22\x25\x27\x5C\x5F]', '\\\0', $string);
    }
} else {
    function
mb_escape(string $string)
    {
        return
preg_replace('~[\x00\x0A\x0D\x1A\x22\x25\x27\x5C\x5F]~u', '\\\$0', $string);
    }
}

?>

Additional characters escaped:

25 = %
5F = _

Bonus function:

The original MySQL `utf8` character-set (for tables and fields) only supports 3-byte sequences.
4-byte characters are not common, but I've had queries fail to execute on 4-byte UTF-8 characters, so you should be using `utf8mb4` wherever possible.

However, if you still want to use `utf8`, you can use the following function to replace all 4-byte sequences.

<?php
// Modified from: https://stackoverflow.com/a/24672780/2726557
function mysql_utf8_sanitizer(string $str)
{
    return
preg_replace('/[\x{10000}-\x{10FFFF}]/u', "\xEF\xBF\xBD", $str);
}
?>

Pick your poison and use at your own risk!
up
34
arnoud at procurios dot nl
16 years ago
Note that this function will NOT escape _ (underscore) and % (percent) signs, which have special meanings in LIKE clauses.

As far as I know there is no function to do this, so you have to escape them yourself by adding a backslash in front of them.
up
11
Anonymous
6 years ago
If you wonder why (besides \, ' and ")  NUL (ASCII 0), \n, \r, and Control-Z are escaped: it is not to prevent sql injection, but to prevent your sql logfile to get unreadable.
up
0
ASchmidt at Anamera dot net
3 months ago
Caution when escaping the % and _ wildcard characters. According to an often overlooked note at the bottom of:

https://dev.mysql.com/doc/refman/5.7/en/string-literals.html#character-escape-sequences

the escape sequences \% and \_ will ONLY be interpreted as % and _, *if* they occur in a LIKE! (Same for MySQL 8.0)

In regular string literals, the escape sequences \% and \_ are treated as those two character pairs. So if those escape sequences appear in a WHERE "=" instead of a WHERE LIKE, they would NOT match a single % or _ character!

Consequently, one MUST use two "escape" functions: The real-escape-string (or equivalent) for regular string literals, and an amended escape function JUST for string literals that are intended to be used in LIKE.
up
-1
Lawrence DOliveiro
3 years ago
Note that the “like” operator requires an *additional* level of escaping for its special characters, *on top of* that performed by mysql_escape_string. But there is no built-in function for performing this escaping. Here is a function that does it:

function escape_sql_wild($s)
  /* escapes SQL pattern wildcards in s. */
  {
    $result = array();
    foreach(str_split($s) as $ch)
      {
        if ($ch == "\\" || $ch == "%" || $ch == "_")
          {
            $result[] = "\\";
          } /*if*/
        $result[] = $ch;
      } /*foreach*/
    return
        implode("", $result);
  } /*escape_sql_wild*/
up
-2
David Spector
2 years ago
I think two additional characters need to be removed or escaped to protect from injection: ` (accent grave) and ; (semicolon). Accent grave could be used to inject into table and key names, terminating them too early (if user input is allowed as table or key names), and semicolon could be used to insert additional statements into an SQL statement. Always use ` (accent grave) to surround table, key, and column names, and always use ' (apostrophe) to surround column values in SQL statements, especially if the names or values can ever contain spaces.
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