I saw on a StackOverflow posting, someone was asking to see how you could use a Zend Framework validator to tell if an IP address was between two addresses. The individual was trying to use Zend_Validate_Between to do the checking. [...] So, assuming that the individual was actually asking about subnet validation, and seeing that I couldn't find a subnet validator for Zend Framework, I wrote a quick one.

The code for the validator is included - an extension of the Zend_Validator class that using the ip2long function to determine the netmask from a given subnet and an "isValid" method to call for the check. There's also a unit test included that you can drop into your test suites.