mysqli::real_escape_string

mysqli::escape_string

mysqli_real_escape_string

(PHP 5, PHP 7)

mysqli::real_escape_string -- mysqli::escape_string -- mysqli_real_escape_string — Protège 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::escape_string ( string $escapestr ) : string

mysqli::real_escape_string ( string $escapestr ) : string

Style procédural

mysqli_real_escape_string ( mysqli $link , string $escapestr ) : string

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

Attention

Securité : 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

link

Seulement en style procédural : Un identifiant de lien retourné par la fonction mysqli_connect() ou par la fonction mysqli_init()

escapestr

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.

Erreurs / Exceptions

L'exécution de cette fonction sans une connexion MySQLi valide passée en argument retourne NULL et émet une erreur de niveau E_WARNING.

Exemples

Exemple #1 Exemple avec mysqli::real_escape_string()

Style orienté objet


<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

/* Vérification de la connexion */
if (mysqli_connect_errno()) {
    printf("Échec de la connexion : %s\n", mysqli_connect_error());
    exit();
}

$mysqli->query("CREATE TEMPORARY TABLE myCity LIKE City");

$city = "'s Hertogenbosch";

/* Cette requête échoue car nous n'avons pas échappé $city */
if (!$mysqli->query("INSERT into myCity (Name) VALUES ('$city')")) {
    printf("Erreur : %s\n", $mysqli->sqlstate);
}

$city = $mysqli->real_escape_string($city);

/* Cette requête, par contre, réussira car nous avons échappé $city */
if ($mysqli->query("INSERT into myCity (Name) VALUES ('$city')")) {
    printf("%d ligne insérée.\n", $mysqli->affected_rows);
}

$mysqli->close();
?>

Style procédural


<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");

/* Vérification de la connexion */
if (mysqli_connect_errno()) {
    printf("Échec de la connexion : %s\n", mysqli_connect_error());
    exit();
}

mysqli_query($link, "CREATE TEMPORARY TABLE myCity LIKE City");

$city = "'s Hertogenbosch";

/* Cette requête échoue car nous n'avons pas échappé $city */
if (!mysqli_query($link, "INSERT into myCity (Name) VALUES ('$city')")) {
    printf("Erreur : %s\n", mysqli_sqlstate($link));
}

$city = mysqli_real_escape_string($link, $city);

/* Cette requête, par contre, réussira car nous avons échappé $city */
if (mysqli_query($link, "INSERT into myCity (Name) VALUES ('$city')")) {
    printf("%d ligne insérée.\n", mysqli_affected_rows($link));
}

mysqli_close($link);
?>

Les exemples ci-dessus vont afficher :

Erreur : 42000
1 ligne insérée.

Notes

Note:
Si vous êtes habitués à utiliser la fonction mysql_real_escape_string(), notez que les arguments de la fonction mysqli_real_escape_string() ne sont pas identiques à ceux de la fonction mysql_real_escape_string(). L'identifiant link est le premier argument pour la fonction mysqli_real_escape_string(), alors que la chaîne à échapper est le premier argument pour la fonction mysql_real_escape_string().

Voir aussi

mysqli_set_charset() - Définit le jeu de caractères par défaut du client
mysqli_character_set_name() - Retourne le jeu de caractères courant pour la connexion

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User Contributed Notes 10 notes

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123

tobias_demuth at web dot de ¶

14 years ago


Note, that if no connection is open, mysqli_real_escape_string() will return an empty string!

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Josef Toman ¶

10 years ago


For percent sign and underscore I use this:
<?php
$more_escaped = addcslashes($escaped, '%_');
?>

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therselman at gmail dot com ¶

3 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!

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dave at mausner.us ¶

9 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.

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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.

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James ¶

4 years ago


To escape for the purposes of having your queries made successfully, and to prevent SQLi (SQL injection)/stored and/or reflected XSS, it's a good idea to go with the basics first, then make sure nothing gets in that can be used for SQLi or stored/reflected XSS, or even worse, loading remote images and scripts.

For example:

<?php
     
     // Assume this is a simple comments form with a name and comment.

     $name = mysqli_real_escape_string($conn, $_POST['name']);
     $comments = mysqli_real_escape_string($conn, $_POST['comments']);

     // Here is where most of the action happens.  But see note below
     // on dumping back out from the database

     // We should use the ENT_QUOTES flag second parameter...
     $name = htmlspecialchars($name);
     $comments = htmlspecialchars($comments);

     $insert_sql = "INSERT INTO tbl_comments ( c_id, c_name, c_comments ) VALUES ( DEFAULT, '" . $name . "', '" . $comments . "')";

     $res = mysqli_query($conn, $insert_sql);
     if ( $res === false ) {
          // Something went wrong, handle it
     }

     // Now output page showing comments
?>

//  Assume we're in a table with each row containing a name and comment

<?php
     
     $res = mysqli_query($conn, "SELECT c_name, c_comments FROM tbl_comments ORDER BY c_name ASC");

     if ( $res === false )
          // Something went wrong

     // Or as you like...
     while ( $row = mysqli_fetch_array($res, MYSQLI_BOTH) ) {
          
          // This will output safe HTML entities if they went in
          // They will be displayed, but not interpreted
          echo "<tr><td>" . $row['c_name'] . "</td>";
          echo "<td>" . $row['c_comments'] . "</td></tr>";

          // BUT, if you make this mistake...
          echo "<tr><td>" . htmlspecialchars_decode($row['c_name']) . "</td>";
          echo "<td>" . htmlspecialchars_decode($row['c_comments']) . "</td></tr>";

          // ... then your entities will reflect back as the characters, so
          // input such as this: "><img src=x onerror=alert('xss')>
          // will display the 'xss' in an alert box in the browser.
     }

     mysqli_free_result($res);
     mysqli_close($conn);
?>

In most cases, you wouldn't want to go way overboard sanitizing untrusted user input, for instance:

<?php
     $my_input = htmlspecialchars( strip_tags($_POST['foo']) );
?>

This will junk a lot of input you might actually want, if you're rolling your own forum or comments section and it's for web developers, for example.  On the other hand, if legitimate users are never going to enter anything other than text, never HTML tags or anything else, it's not a bad idea.

The take-away is that mysqli_real_escape_string() is not good enough, and being overly-aggressive in sanitizing input may not be what you want.

Be aware that in the above example, it will protect you from sqli (run sqlmap on all your input fields and forms to check) but it won't protect your database from being filled with junk, effectively DoS'ing your Web app in the process.

So after protecting against SQLi, even if you're behind CloudFlare and take other measures to protect your databases, there's still effectively a DoS attack that could slow down your Web App for legitimate users and make it a nightmare filled with rubbish that some poor maintainer has to clean out, if you don't take other measures.

So aside from escaping your stings, and protecting against SQLi and stored/reflected XSS, and maliciously loaded images or JS, there's also checking your input to see if it makes sense, so you don't get a database full of rubbish!

It just never ends... :-)

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zanferrari at gmail dot com ¶

6 years ago


When I submit data through Ajax I use a little function to reconvert the encoded chars to their original value. After that I do the escaping. Here the function:

   function my_htmlentities($input){
       $string = htmlentities($input,ENT_NOQUOTES,'UTF-8');
       $string = str_replace('&euro;',chr(128),$string);
       $string = html_entity_decode($string,ENT_NOQUOTES,'ISO-8859-15');
       return $string;
   }

G.Zanferrari

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Anonymous ¶

5 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.

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Lawrence DOliveiro ¶

2 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*/

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-1

David Spector ¶

1 year 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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