A symfony form is made of fields. Each field can be identified by a unique name as we observed in Chapter 1. We connected a widget to each field in order to display it to the user, now let's see how we can apply validation rules to each of the fields.
The validation of each field is done by objects inheriting from the sfValidatorBase class. In order to validate the contact form, we must define validator objects for each of the four fields: name, email, subject, and message. Listing 2-2 shows the implementation of these validators in the form class using the setValidators() method.
Listing 2-2 - Adding Validators to the ContactForm Class
