PHPmysql_real_escape_string () function _ PHP Tutorial

PHPmysql_real_escape_string () function. Define and use special characters in strings used in the mysql_real_escape_string () function to escape SQL statements. The following characters are affected: if x00nrx1a is successful, the function is defined and used.
The mysql_real_escape_string () function escapes special characters in strings used in SQL statements.
The following characters are affected:
\ X00
\ N
\ R
\
'
"
\ X1a
If yes, the function returns the escaped string. If it fails, false is returned.
Syntax
Mysql_real_escape_string (string, connection)
Parameter description
String is required. Specifies the string to be escaped.
Connection is optional. MySQL connection is required. If not specified, use the previous connection.
Description
This function escapes special characters in string and considers the connected current character set. Therefore, it can be safely used for mysql_query ().
Tips and comments
Tip: you can use this function to prevent database attacks.
Example
Example 1
$ Con= mysql_connect ("localhost", "hello", "321 ");
If (! $ Con)
{
Die ('could not connect: '. mysql_error ());
}

// Code for obtaining the user name and password

// Escape the 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
Database attacks. This example shows what will happen if we do not apply the mysql_real_escape_string () function to the user name and password:
$ Con= mysql_connect ("localhost", "hello", "321 ");
If (! $ Con)
{
Die ('could not connect: '. mysql_error ());
}

$ SQL = "SELECT * FROM users
WHERE user = '{$ _ POST ['user']}'
AND password = '{$ _ POST ['pwd']}' ";
Mysql_query ($ SQL );

// Do not check the user name and password. // it can be any content entered by the user, for example:
$ _ POST ['user'] = 'John ';
$ _ POST ['pwd'] = "'OR'' = '";

// Some code...

Mysql_close ($ con );
?>
The SQL query will be like this:
SELECT * FROM users
WHERE user = 'John' AND password = ''OR'' =''
This means that any user can log on without entering a valid password.
Example 3
The correct method to prevent database attacks:
Function check_input ($ value)
{
// Remove the slash
If (get_magic_quotes_gpc ())
{
$ Value = stripslashes ($ value );
}
// If it is not a number, enclose it with quotation marks.
If (! Is_numeric ($ value ))
{
$ Value = "'". mysql_real_escape_string ($ value )."'";
}
Return $ value;
}

$ Con= mysql_connect ("localhost", "hello", "321 ");
If (! $ Con)
{
Die ('could not connect: '. mysql_error ());
}

// Perform a safe SQL statement
$ 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 );
?>

Author "Shore"

Use the mysql_real_escape_string () function to escape special characters in strings used in SQL statements. The following characters are affected: \ x00 \ n \ r \ x1a. if the operation is successful, this function returns...