mysql_real_escape_string

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

Waarschuwing: > mysqli_real_escape_string``PDO::quote

string **mysql_real_escape_string** string $unescaped_string resource $link_identifier

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

calls MySQL's library function

mysql_real_escape_string, which prepends backslashes to the following characters: , , , , , and . mysql_real_escape_string``\x00``\n``\r``\``'``"``\x1a

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

Let op: > ### Security: the default character set
The character set must be set either at the server level, or with
the API function  for it to affect
. See the concepts section
on  for
more information.
mysql_set_charset``mysql_real_escape_stringcharacter sets

unescaped_stringThe string that is to be escaped.

Returns the escaped string, or false on error.

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

Voorbeeld: Simple 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));
?>

Voorbeeld: 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);
?>

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 = ''"

Voorbeeld: 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.

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

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

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

mysql_set_charset``mysql_client_encoding

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mysql_real_escape_string

mysql_real_escape_string

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