mysqli::real_escape_string

mysqli_real_escape_string

(PHP 5, PHP 7)

mysqli::real_escape_string -- mysqli_real_escape_stringEscapa los caracteres especiales de una cadena para usarla en una sentencia SQL, tomando en cuenta el conjunto de caracteres actual de la conexión

Descripción

Estilo orientado a objetos

mysqli::escape_string ( string $escapestr ) : string
mysqli::real_escape_string ( string $escapestr ) : string

Estilo por procedimientos

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

Esta función se usa para crear una cadena SQL legal que se puede usar en una sentencia SQL. La cadena dada es codificada a una cadena SQL escapada, tomando en cuenta el conjunto de caracteres actual de la conexión.

Precaución

Seguridad: el conjunto de caracteres predeterminado

El conjunto de caracteres debe ser establecido a nivel del servidor, o con la función mysqli_set_charset() de la API para que afecte a mysqli_real_escape_string(). Véase la sección de conceptos sobre conjuntos de caracteres para más información.

Parámetros

link

Sólo estilo por procediminetos: Un identificador de enlace devuelto por mysqli_connect() o mysqli_init()

escapestr

La cadena a escapar.

Los caracteres codificados son NUL (ASCII 0), \n, \r, \, ', ", y Control-Z.

Valores devueltos

Devuelve una cadena escapada.

Ejemplos

Ejemplo #1 Ejemplo de mysqli::real_escape_string()

Estilo orientado a objetos

<?php
$mysqli 
= new mysqli("localhost""mi_usuario""mi_contraseña""world");

/* verificar la conexión */
if (mysqli_connect_errno()) {
    
printf("Falló la conexión: %s\n"mysqli_connect_error());
    exit();
}

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

$ciudad "'s Hertogenbosch";

/* esta consulta fallará debido a que no escapa $ciudad */
if (!$mysqli->query("INSERT into miCiudad (Name) VALUES ('$ciudad')")) {
    
printf("Error: %s\n"$mysqli->sqlstate);
}

$ciudad $mysqli->real_escape_string($ciudad);

/* esta consulta con $ciudad escapada funcionará */
if ($mysqli->query("INSERT into miCiudad (Name) VALUES ('$ciudad')")) {
    
printf("%d fila insertada.\n"$mysqli->affected_rows);
}

$mysqli->close();
?>

Estilo por procedimientos

<?php
$enlace 
mysqli_connect("localhost""mi_usuario""mi_contraseña""world");

/* verificar la conexión */
if (mysqli_connect_errno()) {
    
printf("Falló la conexión: %s\n"mysqli_connect_error());
    exit();
}

mysqli_query($enlace"CREATE TEMPORARY TABLE miCiudad LIKE City");

$ciudad "'s Hertogenbosch";

/* esta consulta fallará debido a que no escapa $ciudad */
if (!mysqli_query($enlace"INSERT into miCiudad (Name) VALUES ('$ciudad')")) {
    
printf("Error: %s\n"mysqli_sqlstate($enlace));
}

$ciudad mysqli_real_escape_string($enlace$ciudad);

/* esta consulta con $ciudad escapada funcionará */
if (mysqli_query($enlace"INSERT into miCiudad (Name) VALUES ('$ciudad')")) {
    
printf("%d fila insertada.\n"mysqli_affected_rows($enlace));
}

mysqli_close($enlace);
?>

El resultado de los ejemplos sería:

Error: 42000
1 fila insertada.

Notas

Nota:

Para quienes estén acostumbrados a usar mysql_real_escape_string(), se ha de observar que el argumento de mysqli_real_escape_string() difiere de lo que espera mysql_real_escape_string(). El identificador enlace va primero en mysqli_real_escape_string(), mientras que la cadena a escapar va primero en mysql_real_escape_string().

Ver también

add a note add a note

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
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!
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
18 days 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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