Validation of Lead record fields

Hello,

I wrote some functions for sending a lead record to Netsuite using web-form and php script - user fills the form, clicks on "submit" and its sent to Netsuite using soap calls. However, there are a few problems with validation - phone/fax fields in Netsuite accepts only numbers with at least seven digits and return an error if its not valid. What is the best way in general to implement such form, has anyone here done it with php or any other language? How should phone/fax fields handled - is it possible to change validation rules in Netsuite or better