|
Home
iRate! IceMelon IM Tutorials Headlines CoolSites PHP Functions |
Most Referenced Functions » google_pagerank() » preg_replace() » imagecreatefrompng() » site_pageranks() » imagepng() » imagedestroy() » imagestring() » imagecolorallocate() » htmlentities() » fopen() » preg_match() » header() » getimagesize() » htmlspecialchars() » ob_start() » session_start() » strstr() » ob_flush() » preg_match_all() » strpos() » setcookie() » flush() » str_replace() » array2vars() » nl2br() » preg_split() » ereg() » urlencode() » ereg_replace() » readgzfile() Become a sponsor for $15/month. Link is sitewide - PR5 homepage, 20+ PR4 pages, 90+ PR3 pages. Email dave[AT]icemelon[D0T]c0m. |
PHP Functions
Function: mysql_real_escape_string (PHP 4 >= 4.3.0, PHP 5) mysql_real_escape_string -- Escapes special characters in a string for use in a SQL statementDescriptionstring mysql_real_escape_string ( string unescaped_string [, resource link_identifier] )Escapes special characters in the unescaped_string , taking into account the current character set of the connection so that it is safe to place it in a mysql_query() . If binary data is to be inserted, this function must be used. mysql_real_escape_string() calls MySQL's library function mysql_real_escape_string, which prepends backslashes to the following characters: \x00 , \n , \r , \ , ' , " and \x1a . This function must always (with few exceptions) be used to make data safe before sending a query to MySQL. Parameters
unescaped_string The string that is to be escaped. link_identifierThe MySQL connection. If the link identifier is not specified, the last link opened by mysql_connect() is assumed. If no such link is found, it will try to create one as if mysql_connect() was called with no arguments. If by chance no connection is found or established, an E_WARNING level warning is generated. Return ValuesReturns the escaped string, or FALSE on error. Examples
Example 1. Simple mysql_real_escape_string() example <?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. An example SQL Injection Attack <?php // 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); // We didn't check $_POST['password'], it could be anything the user wanted! For example: $_POST['username'] = 'aidan'; $_POST['password'] = "' OR ''='"; // This means the query sent to MySQL would be: echo $query; ?> The query sent to MySQL: SELECT * FROM users WHERE name='aidan' AND password='' OR ''='' This would allow anyone to log in without a valid password.
Example 3. A "Best Practice" query Using mysql_real_escape_string() around each variable prevents SQL Injection. This example demonstrates the "best practice" method for querying a database, independent of the Magic Quotes setting. <?php // Quote variable to make safe function quote_smart($value) { // Stripslashes if (get_magic_quotes_gpc()) { $value = stripslashes($value); } // Quote if not integer if (!is_numeric($value)) { $value = "'" . mysql_real_escape_string($value) . "'"; } return $value; } // Connect $link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password') OR die(mysql_error()); // Make a safe query $query = sprintf("SELECT * FROM users WHERE user=%s AND password=%s", quote_smart($_POST['username']), quote_smart($_POST['password'])); mysql_query($query); ?> The query will now execute correctly, and SQL Injection attacks will not work. NotesNote: 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 . Related Function(s) |