Everyone knows that you should filter your inputs most of the good programmers do it but when you are working with a large team of programmers on an open source project things slip up, errors do creep in, at times like this you wish for a mechanism which would prevent your team from making such mistakes, some thing which forces them to declare their intent.

One solution he mentions is the input_filter extension for PHP5, but this doesn't help most users since it's normally off by default and PHP5-only. The other solution, Inspekt, a modified version of the Zend_Filter_input component of the Zend Framework. An example is included and a list of filtering methods is too (like getAlnum, getDigits and getInt).

The most secure application is one with no connection to the outside world.

As we've covered, you can't really disconnect the network from your web server if you are building web applications. You can however, carefully consider which servers need to be connected to the outside world and which can be inside your firewall. Beyond that, you can also evaluate how those servers that have to remain outside your firewall communicate with the ones inside.

No, his suggestion is not to take your application "off the grip" but more to limit access to things like database servers to help protect the data that lives inside it.