MySQL 函数
PHP Manual

mysql_real_escape_string

(PHP 4 >= 4.3.0, PHP 5)

mysql_real_escape_string — 转义 SQL 语句中使用的字符串中的特殊字符，并考虑到连接的当前字符集

Warning

本扩展自 PHP 5.5.0 起已废弃，并在将来会被移除。应使用 MySQLi 或 PDO_MySQL 扩展来替换之。参见 MySQL：选择 API 指南以及相关 FAQ 以获取更多信息。用以替代本函数的有：

说明

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

本函数将 unescaped_string 中的特殊字符转义，并计及连接的当前字符集，因此可以安全用于 mysql_query()。

mysql_real_escape_string() 调用mysql库的函数 mysql_real_escape_string, 在以下字符前添加反斜杠: \x00, \n, \r, \, ', " 和 \x1a.

为了安全起见，在像MySQL传送查询前，必须调用这个函数（除了少数例外情况）。

Caution

安全提示: 默认字符集

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.

参数

unescaped_string

The string that is to be escaped.

link_identifier

MySQL 连接。如不指定连接标识，则使用由 mysql_connect() 最近打开的连接。如果没有找到该连接，会尝试不带参数调用 mysql_connect() 来创建。如没有找到连接或无法建立连接，则会生成 E_WARNING 级别的错误。

返回值

Returns the escaped string, or FALSE on error.

错误／异常

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.

范例

Example #1 mysql_real_escape_string() 例子

<?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);
?>

以上例程的输出类似于：

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.

注释

Note:

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.

Note:

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.

Note:

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

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

参见

MySQL 函数
PHP Manual