mysql_real_escape_string

(PHP 4 >= 4.3.0, PHP 5)

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说锟斤拷

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

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Caution

锟斤拷全锟斤拷示: 默锟斤拷锟街凤拷锟斤拷

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.

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unescaped_string

The string that is to be escaped.

link_identifier

MySQL 锟斤拷锟接★拷锟界不指锟斤拷锟斤拷锟接憋拷识锟斤拷锟斤拷使锟斤拷锟斤拷 mysql_connect() 锟斤拷锟斤拷蚩锟斤拷锟斤拷印锟斤拷锟斤拷没锟斤拷锟揭碉拷锟斤拷锟斤拷锟接ｏ拷锟结尝锟皆诧拷锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷 mysql_connect() 锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷没锟斤拷锟揭碉拷锟斤拷锟接伙拷锟睫凤拷锟斤拷锟斤拷锟斤拷锟接ｏ拷锟斤拷锟斤拷锟斤拷锟� E_WARNING 锟斤拷锟斤拷拇锟斤拷锟�

锟斤拷锟斤拷值

Returns the escaped string, or FALSE on error.

锟斤拷锟斤拷锟届常

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.

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Example #1 mysql_real_escape_string() 锟斤拷锟斤拷

<?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);
?>

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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.

注锟斤拷

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.

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