Server Side Validation For Joomla Registration Form?

Question

I need to do a php server side validation for the username field on the standard registration form (Joomla 2.5). How is this achieved please, and in which file do I add it to? Thanks.

Answer 1

I recommend you read Joomla Developer documentation. Also read this docs to find out how to use Joomla Forms with client and server side validation.

Here is a more general doc: Joomla Server-side form validation