mysql_real_escape_string() 函（mysql_real_escape_string() 函数）- PHP

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PHP 中的 mysql_real_escape_string() 函

出处:互联网 整理: 软晨网（RuanChen.com） 发布: 2009-03-04 浏览: 586 ::

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Definition and Usage
定义和用法

The mysql_real_escape_string() function escapes special characters in a string for use in an SQL statement
mysql_real_escape_string()函数的作用是：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。

The following characters are affected:
可对下列字符进行操作：

This function returns the escaped string on success, or FALSE on failure.
如果函数执行成功，将返回转义后的字符串；如果执行失败将返回False。

Syntax
语法

mysql_real_escape_string(string,connection)

Parameter参数	Description描述
string	Required. Specifies the string to be escaped 必要参数。制定需要执行转义操作的字符串
connection	Optional. Specifies the MySQL connection. If not specified, the last connection opened by mysql_connect() or mysql_pconnect() is used. 可选参数。指定MySQL连接。如果不指定该参数，那将默认使用通过mysql_connect()函数或mysql_pconnect()函数最后一次打开的连接

Tips and Notes
注意点

Note: Use this function to prevent database attack!
注意：可以使用该函数来阻止数据库被攻击。

Example 1
案例1

<?php
$con = mysql_connect("localhost", "peter", "abc123");
if (!$con) { die('Could not connect: ' . mysql_error()); }

// some code to get username and password

// escape username and password for use in SQL
$user = mysql_real_escape_string($user);
$pwd = mysql_real_escape_string($pwd));

$sql = "SELECT * FROM users WHERE
user='" . $user . "' AND password='" . $pwd . "'"

// more code

mysql_close($con);
?>

Example 2
案例2

Database attack. This example demonstrates what could happen if we do not use the mysql_real_escape_string() function on the username and password:
下面将列举数据库被攻击的状况。这个案例演示了如果我们在不输入用户名和密码并使用mysql_real_escape_string()函数的情况下将会发生什么：

<?php
$con = mysql_connect("localhost", "peter", "abc123");
if (!$con) { die('Could not connect: ' . mysql_error()); }

$sql = "SELECT * FROM users
WHERE user='{$_POST['user']}'
AND password='{$_POST['pwd']}'";
mysql_query($sql);

// We didn't check username and password.
// Could be anything the user wanted! Example:
$_POST['user'] = 'john';
$_POST['pwd'] = "' OR ''='";

// some code

mysql_close($con);
?>

The SQL sent would be:
发送的SQL将会是如下信息：

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

This means that anyone could log in without a valid password!
上述代码意味着任何人都不能通过无效的密码登陆。

Example 3
案例3

The correct way to do it to prevent database attack:
防止数据库被攻击的正确做法如下：

<?php
function check_input($value)
{
// Stripslashes
if (get_magic_quotes_gpc()) { $value = stripslashes($value); }
// Quote if not a number
if (!is_numeric($value)) { $value = "'" . mysql_real_escape_string($value) . "'"; }
return $value;
}

$con = mysql_connect("localhost", "peter", "abc123");
if (!$con) { die('Could not connect: ' . mysql_error()); }

// Make a safe SQL
$user = check_input($_POST['user']);
$pwd = check_input($_POST['pwd']);
$sql = "SELECT * FROM users WHERE
user=$user AND password=$pwd";

mysql_query($sql);

mysql_close($con);
?>

PHP 中的 mysql_real_escape_string() 函

Definition and Usage 定义和用法

Syntax 语法

Tips and Notes 注意点

Example 1 案例1

Example 2 案例2