using custom function in object for validation rule in HTML_QuickForm

I saw some sample code where someone extended the HTML_QuickForm object to create a form. I am trying to duplicate the same setup with a login class. What I want to do is create custom functions in the object for validating the password and username. I am trying to add this, but can't get it to work. I get the error: *Fatal error*: Call to undefined function: $this->process_passwd() in */usr/share/php/HTML/QuickForm/Rule/Callback.php* on line *70** The register rule I am trying is this: $this->registerRule('processpasswd', 'callback', '$this->process_passwd'); Since $this is an extended quickform object I thought it might work with my custom process_passwd function. Any ideas how I could make this work? Code layout: class login extends HTML_QuickForm { show_login_form() {

      // all the code for generating the form is in here including registerRule()

} process_passwd($data) {

      // code for checking the password is valid in this function

} } Thank Rick *