(PHP 4 >= 4.3.0, PHP 5)
mysql_real_escape_string — 将字符串中的特殊字符进行转义，以在 SQL 语句中使用
本扩展自 PHP 5.5.0 起已废弃，并在自 PHP 7.0.0 开始被移除。应使用 MySQLi 或 PDO_MySQL 扩展来替换之。参见 MySQL：选择 API 指南来获取更多信息。用以替代本函数的有：
考虑到连接的当前字符集，对 unescaped_string 进行特殊字符转义，以便安全地将其放置在 mysql_query() 中。如果要插入二进制数据，则必须使用此函数。
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线：\x00、\n、\r、\、'、"
和 \x1a.
在向 MySQL 发送查询之前，必须始终（有少数例外）使用此函数来确保数据的安全。
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.
unescaped_stringThe string that is to be escaped.
link_identifierMySQL
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。
Returns the escaped string, or false on error.
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.
示例 #1 简单 mysql_real_escape_string() 示例
<?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));
?>
示例 #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);
?>以上示例的输出类似于：
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 = ''"
示例 #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.
注意:
A MySQL connection is required before using mysql_real_escape_string() otherwise an error of level
E_WARNINGis generated, andfalseis returned. Iflink_identifierisn't defined, the last MySQL connection is used.
注意:
If this function is not used to escape data, the query is vulnerable to SQL Injection Attacks.
注意: mysql_real_escape_string() does not escape
%and_. These are wildcards in MySQL if combined withLIKE,GRANT, orREVOKE.