Php/docs/function.mysql-real-escape-string

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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 指南以及相关 FAQ 来获取更多信息。用以替代本函数的有：


说明

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

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 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


取自“https://cainiaojiaocheng.com/index.php?title=Php/docs/function.mysql-real-escape-string&oldid=6047”
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