Modify form validation in registration in joomla 2.5

Question

How do you get to show a warning message that a field is required to be filled with the following rules in registration module in joomla 2.5?

If I click Register button without following the rules (like entering a password with a minimum of 4 characters and submitting the form with empty fields) the form won't submit and will just change its color into red without displaying any warning message.

Also I've been trying to find the file where error message is in registration, but can't find it in com_users component.

BOTTOMLINE: What I want to do is, when user clicks Register button without following the rules (like entering a password with a minimum of 4 characters) a warning message will be displayed saying "Password should be minimum of 4chars", something like that.

Answer 1

1. You should know that "The Messages" are found in the language files. For your case, the com_users component, they are in "/language/THE-LANGUAGE(en-GB or something different)/en-GB.com_users.ini". Of course, keep in mind that you should use language constant overrides (Admin->Languages Manager->Overrides).

2. If you want to change the client side validations for the registration form you should create a template override for that particular view/layout.
By this I mean:
1. copy /components/com_users/views/registration/tmpl/default.php to a folder in your template: /templates/YOUR_TEMPLATE/html/com_users/registration/default.php
2. modify the html of the file so that it fits your needs.
3. attach the client-side validation (javascript code) ... from that override using JDocument::adScriptDeclaration();

3. For the server side validation you need to create a User plugin that takes advantage of the "onUserBeforeSave" event triggered in the users component. Further reading can be found here.