mysqli::real_escape_string

mysqli_real_escape_string

(PHP 5)

mysqli::real_escape_string -- mysqli_real_escape_stringEscapes special characters in a string for use in an SQL statement, taking into account the current charset of the connection

Description

Object oriented style

string mysqli::escape_string ( string $escapestr )
string mysqli::real_escape_string ( string $escapestr )

Procedural style

string mysqli_real_escape_string ( mysqli $link , string $escapestr )

This function is used to create a legal SQL string that you can use in an SQL statement. The given string is encoded to an escaped SQL string, taking into account the current character set of the connection.

Caution

Security: the default character set

The character set must be set either at the server level, or with the API function mysqli_set_charset() for it to affect mysqli_real_escape_string(). See the concepts section on character sets for more information.

Parameters

link

Procedural style only: A link identifier returned by mysqli_connect() or mysqli_init()

escapestr

The string to be escaped.

Characters encoded are NUL (ASCII 0), \n, \r, \, ', ", and Control-Z.

Return Values

Returns an escaped string.

Examples

Example #1 mysqli::real_escape_string() example

Object oriented style

<?php
$mysqli 
= new mysqli("localhost""my_user""my_password""world");

/* check connection */
if (mysqli_connect_errno()) {
    
printf("Connect failed: %s\n"mysqli_connect_error());
    exit();
}

$mysqli->query("CREATE TEMPORARY TABLE myCity LIKE City");

$city "'s Hertogenbosch";

/* this query will fail, cause we didn't escape $city */
if (!$mysqli->query("INSERT into myCity (Name) VALUES ('$city')")) {
    
printf("Error: %s\n"$mysqli->sqlstate);
}

$city $mysqli->real_escape_string($city);

/* this query with escaped $city will work */
if ($mysqli->query("INSERT into myCity (Name) VALUES ('$city')")) {
    
printf("%d Row inserted.\n"$mysqli->affected_rows);
}

$mysqli->close();
?>

Procedural style

<?php
$link 
mysqli_connect("localhost""my_user""my_password""world");

/* check connection */
if (mysqli_connect_errno()) {
    
printf("Connect failed: %s\n"mysqli_connect_error());
    exit();
}

mysqli_query($link"CREATE TEMPORARY TABLE myCity LIKE City");

$city "'s Hertogenbosch";

/* this query will fail, cause we didn't escape $city */
if (!mysqli_query($link"INSERT into myCity (Name) VALUES ('$city')")) {
    
printf("Error: %s\n"mysqli_sqlstate($link));
}

$city mysqli_real_escape_string($link$city);

/* this query with escaped $city will work */
if (mysqli_query($link"INSERT into myCity (Name) VALUES ('$city')")) {
    
printf("%d Row inserted.\n"mysqli_affected_rows($link));
}

mysqli_close($link);
?>

The above examples will output:

Error: 42000
1 Row inserted.

Notes

Note:

For those accustomed to using mysql_real_escape_string(), note that the arguments of mysqli_real_escape_string() differ from what mysql_real_escape_string() expects. The link identifier comes first in mysqli_real_escape_string(), whereas the string to be escaped comes first in mysql_real_escape_string().

See Also

Коментарии

Note that this function will NOT escape _ (underscore) and % (percent) signs, which have special meanings in LIKE clauses. 

As far as I know there is no function to do this, so you have to escape them yourself by adding a backslash in front of them.
2004-10-07 12:05:22
http://php5.kiev.ua/manual/ru/mysqli.real-escape-string.html
Автор:
For percent sign and underscore I use this:
<?php
$more_escaped 
addcslashes($escaped'%_');
?>
2010-02-26 08:14:00
http://php5.kiev.ua/manual/ru/mysqli.real-escape-string.html
Автор:
You can avoid all character escaping issues (on the PHP side) if you use prepare() and bind_param(), as an alternative to placing arbitrary string values in SQL statements.  This works because bound parameter values are NOT passed via the SQL statement syntax.
2011-02-25 09:48:13
http://php5.kiev.ua/manual/ru/mysqli.real-escape-string.html
Автор:
If you wonder why (besides \, ' and ")  NUL (ASCII 0), \n, \r, and Control-Z are escaped: it is not to prevent sql injection, but to prevent your sql logfile to get unreadable.
2015-03-25 23:20:02
http://php5.kiev.ua/manual/ru/mysqli.real-escape-string.html
Presenting several UTF-8 / Multibyte-aware escape functions.

These functions represent alternatives to mysqli::real_escape_string, as long as your DB connection and Multibyte extension are using the same character set (UTF-8), they will produce the same results by escaping the same characters as mysqli::real_escape_string.

This is based on research I did for my SQL Query Builder class:
https://github.com/twister-php/sql

<?php
/**
 * Returns a string with backslashes before characters that need to be escaped.
 * As required by MySQL and suitable for multi-byte character sets
 * Characters encoded are NUL (ASCII 0), \n, \r, \, ', ", and ctrl-Z.
 *
 * @param string $string String to add slashes to
 * @return $string with `\` prepended to reserved characters 
 *
 * @author Trevor Herselman
 */
if (function_exists('mb_ereg_replace'))
{
    function 
mb_escape(string $string)
    {
        return 
mb_ereg_replace('[\x00\x0A\x0D\x1A\x22\x27\x5C]''\\\0'$string);
    }
} else {
    function 
mb_escape(string $string)
    {
        return 
preg_replace('~[\x00\x0A\x0D\x1A\x22\x27\x5C]~u''\\\$0'$string);
    }
}

?>

Characters escaped are (the same as mysqli::real_escape_string):

00 = \0 (NUL)
0A = \n
0D = \r
1A = ctl-Z
22 = "
27 = '
5C = \

Note: preg_replace() is in PCRE_UTF8 (UTF-8) mode (`u`).

Enhanced version:

When escaping strings for `LIKE` syntax, remember that you also need to escape the special characters _ and %

So this is a more fail-safe version (even when compared to mysqli::real_escape_string, because % characters in user input can cause unexpected results and even security violations via SQL injection in LIKE statements):

<?php

/**
 * Returns a string with backslashes before characters that need to be escaped.
 * As required by MySQL and suitable for multi-byte character sets
 * Characters encoded are NUL (ASCII 0), \n, \r, \, ', ", and ctrl-Z.
 * In addition, the special control characters % and _ are also escaped,
 * suitable for all statements, but especially suitable for `LIKE`.
 *
 * @param string $string String to add slashes to
 * @return $string with `\` prepended to reserved characters 
 *
 * @author Trevor Herselman
 */
if (function_exists('mb_ereg_replace'))
{
    function 
mb_escape(string $string)
    {
        return 
mb_ereg_replace('[\x00\x0A\x0D\x1A\x22\x25\x27\x5C\x5F]''\\\0'$string);
    }
} else {
    function 
mb_escape(string $string)
    {
        return 
preg_replace('~[\x00\x0A\x0D\x1A\x22\x25\x27\x5C\x5F]~u''\\\$0'$string);
    }
}

?>

Additional characters escaped:

25 = %
5F = _

Bonus function:

The original MySQL `utf8` character-set (for tables and fields) only supports 3-byte sequences.
4-byte characters are not common, but I've had queries fail to execute on 4-byte UTF-8 characters, so you should be using `utf8mb4` wherever possible.

However, if you still want to use `utf8`, you can use the following function to replace all 4-byte sequences.

<?php
// Modified from: https://stackoverflow.com/a/24672780/2726557
function mysql_utf8_sanitizer(string $str)
{
    return 
preg_replace('/[\x{10000}-\x{10FFFF}]/u'"\xEF\xBF\xBD"$str);
}
?>

Pick your poison and use at your own risk!
2017-07-19 23:22:46
http://php5.kiev.ua/manual/ru/mysqli.real-escape-string.html
Автор:
Note that the “like” operator requires an *additional* level of escaping for its special characters, *on top of* that performed by mysql_escape_string. But there is no built-in function for performing this escaping. Here is a function that does it:

function escape_sql_wild($s)
  /* escapes SQL pattern wildcards in s. */
  {
    $result = array();
    foreach(str_split($s) as $ch)
      {
        if ($ch == "\\" || $ch == "%" || $ch == "_")
          {
            $result[] = "\\";
          } /*if*/
        $result[] = $ch;
      } /*foreach*/
    return
        implode("", $result);
  } /*escape_sql_wild*/
2017-12-13 05:56:47
http://php5.kiev.ua/manual/ru/mysqli.real-escape-string.html
Caution when escaping the % and _ wildcard characters. According to an often overlooked note at the bottom of:
 
https://dev.mysql.com/doc/refman/5.7/en/string-literals.html#character-escape-sequences

the escape sequences \% and \_ will ONLY be interpreted as % and _, *if* they occur in a LIKE! (Same for MySQL 8.0)

In regular string literals, the escape sequences \% and \_ are treated as those two character pairs. So if those escape sequences appear in a WHERE "=" instead of a WHERE LIKE, they would NOT match a single % or _ character!

Consequently, one MUST use two "escape" functions: The real-escape-string (or equivalent) for regular string literals, and an amended escape function JUST for string literals that are intended to be used in LIKE.
2021-03-30 19:45:17
http://php5.kiev.ua/manual/ru/mysqli.real-escape-string.html

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