title: Is it possible to create custom form field attributes in Symfony 2?
body: <p>In Symfony2 form component is it possible to create custom attributes?</p>
  
  <p>The reason why I ask is because I'm working on a certain edge case where read_only will not be sufficient. </p>
  
  <p>Here is the scenario: I need to bind data based on the outcome of some external logic parsing. This is crucial because I may have fields that are disabled by default but based on the external logic the fields may be activated. I cannot use client scripting to produce this outcome, it has to be disabled in the form attribute.</p>
  
  <p>If I start with the field as read_only, it will be disabled, but I will never be able to bind data to it. So given the outcome of my aforementioned external logic, I will not be able to use read_only. So this leaves me with no other option but using a different attribute which will make the field disabled.</p>
  
  <p>Is it possible to create a custom attribute to produced this disabled effect?</p>