hi, i need help creating a validation rule to test multiple fields at one time and not just one field at a time.

My goel is to test and make sure that first_name, last_name and email is all unique!!!

I have seen the validation rule for unique email but it test only one field.

My question would be how do I start a function and pass all three values at the same time when the submit button is pressed

//code//
...
$db =& JFactory::getDBO();
$query = "SELECT * FROM jos_user WHERE first_name = fname AND last_name = lname AND email = uemail";
$db->setQuery($query);
$db->query();
$num_row = $db->getNumRows();

if($num_row <0)
return false;
return true;
//code//