Can someone point me to information/documentation regarding options to review data submitted from a form before updating a record? Here's my scenario. 

We are creating a custom PHP registration form that we will send to existing customers. The form will be pre-populated with data from their contact record. We want to allow the client to modify/update data in some fields as appropriate but would like to review the data before updating the contact record. 

What's the best way to do this? Is there a standard Zoho CRM feature to enable this?