SQL Injection in PHP
SQL Injection is a method in which an attacker inserts malicious code into queries that run on your database.
look at this example:
$query = “SELECT login_id FROM users WHERE user=’$user’ AND pwd=’$pw'”;
Anyone can log in as any user, using a query string like
http://www.wetala.com/login.php?user=admin’%20OR%20(user=’&pwd=’) %20OR%20user=’, which effectively calls the following statements:
$query = “SELECT login_id FROM users WHERE user=’admin’ OR (user = ” AND pwd=”) OR user=””; mysql_query($query);
It’s even simpler with the URL
http://example.com/login.php? user=admin’%23, which executes the query SELECT login_id FROM users WHERE user=’admin’#’ AND pwd=”.
the # marks the beginning of a comment in SQL. Again, it’s a simple attack. Fortunately, it’s also easy to prevent. You can sanitize the input using the addslashes() function that adds a slash before every single quote (‘), double quote (“), backslash (\), and NUL (\0). Other functions are available to sanitize input, such as strip_tags().