OK, what you're doing is a start, but there are other things you can do. To start with this article
http://www.askbee.net/articles/php/SQL_Injection/sql_injection.htmlalready discusses some of what you are doing, but read it anyway for clarification and background.
Next - quote everything. Many people never quote integers
select * from myTable where myint = $intNumber
Instead do this
select * from myTable where myint = '$intNumber'
In your PHP force types, so if that statement was generated by PHP, rather than the above, do this
mysql_query("select * from myTable where myint = '". intval($intNumber) ."' ");
http://www.php.net/intvalhttp://www.php.net/floatvalNever EVER trust input. Read what I wrote a few days ago
http://www.experts-exchange.com/Web_Development/Web_Languages-Standards/PHP/Q_24942604.htmlScroll down to the bottom. Ray makes some good points as well.