Escapes special characters in a string for use in an SQL statement

# mysql_real_escape_string

(PHP 4 >= 4.3.0, PHP 5)

mysql_real_escape_string — Escapes special characters in a string for use in an SQL statement

Avertizare

Această extensie a devenit învechită în PHP 5.5.0 și a fost eliminată în PHP 7.0.0. În locul ei trebuie utilizată extensia MySQLi sau PDO_MySQL. Accesați de asemenea ghidul MySQL: selectarea unei API și FAQ asociat pentru informații suplimentare. Variante alternative pentru această funcție includ:

- mysqli_real_escape_string()
- PDO::quote()

### Descrierea

mysql_real_escape_string ( string `$unescaped_string` [, resource `$link_identifier` = NULL ] ) : string

Escapes special characters in the `unescaped_string`, taking into account the current character set of the connection so that it is safe to place it in a mysql_query(). If binary data is to be inserted, this function must be used.

mysql_real_escape_string() calls MySQL's library function mysql_real_escape_string, which prepends backslashes to the following characters: \x00, \n, \r, \, ', " and \x1a.

This function must always (with few exceptions) be used to make data safe before sending a query to MySQL.

Precauţie

# Security: the default character set

The character set must be set either at the server level, or with the API function mysql_set_charset() for it to affect mysql_real_escape_string(). See the concepts section on character sets for more information.

### Parametri

`unescaped_string`

  The string that is to be escaped.

`link_identifier`

  Conexiunea MySQL. Dacă identificatorul legăturii nu este specificat, se presupune că este ultima legătură deschisă cu ajutorul mysql_connect(). Dacă nu este găsită nici o astfel de legătură, se va încerca crearea uneia prin apelul mysql_connect () fără argumente. În caz că nici o conexiune nu este găsită sau stabilită, se va genera o eroare de nivelul `E_WARNING`.

### Valorile întoarse

Returns the escaped string, or `FALSE` on error.

### Erori/Excepții

Executing this function without a MySQL connection present will also emit `E_WARNING` level PHP errors. Only execute this function with a valid MySQL connection present.

### Exemple

Example #1 Simple mysql_real_escape_string() example

`<?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 mysql_real_escape_string() requires a connection example

This example demonstrates what happens if a MySQL connection is not present when calling this function.

`<?php
// We have not connected to MySQL
$lastname = "O'Reilly";
$_lastname = mysql_real_escape_string($lastname);
$query = "SELECT * FROM actors WHERE last_name = '$_lastname'";
var_dump($_lastname);
var_dump($query);
?>`

Exemplul de mai sus va afișa ceva similar cu:

    Warning: mysql_real_escape_string(): No such file or directory in /this/test/script.php on line 5
    Warning: mysql_real_escape_string(): A link to the server could not be established in /this/test/script.php on line 5

    bool(false)
    string(41) "SELECT * FROM actors WHERE last_name = ''"

Example #3 An example SQL Injection Attack

`<?php
// We didn't check $_POST['password'], it could be anything the user wanted! For example:
$_POST['username'] = 'aidan';
$_POST['password'] = "' OR ''='";
// 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);
// This means the query sent to MySQL would be:
echo $query;
?>`

The query sent to MySQL:

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

This would allow anyone to log in without a valid password.

### Note

> Notă:

> A MySQL connection is required before using mysql_real_escape_string() otherwise an error of level `E_WARNING` is generated, and `FALSE` is returned. If `link_identifier` isn't defined, the last MySQL connection is used.

> Notă:

> If magic_quotes_gpc is enabled, first apply stripslashes() to the data. Using this function on data which has already been escaped will escape the data twice.

> Notă:

> If this function is not used to escape data, the query is vulnerable to SQL Injection Attacks.

> Notă: mysql_real_escape_string() does not escape % and _. These are wildcards in MySQL if combined with LIKE, GRANT, or REVOKE.

### A se vedea și

- mysql_set_charset() - Sets the client character set
- mysql_client_encoding() - Întoarce denumirea setului de caractere
- addslashes() - Quote string with slashes
- stripslashes() - Un-quotes a quoted string
- The magic_quotes_gpc directive
- The magic_quotes_runtime directive