If you've ever used the drupal views module, chances are at some point you've needed to suppress any output until AFTER the user has made a selection from one of your exposed filters. Views actually DOES make this possible, but it's not exactly self-evident. I'm going to run you through a quick "howto" on this as I'm sure many people have needed it at some point.
As I mentioned above, this is possible but not particularly self-evident. Views has a number of different "global" group items. The most common of these is probably the Random Sort. Within arguments you also have another member of the global group, the global NULL argument. This is basically a way of attaching your own rudimentary argument to a view. Through the use of the default value (as custom php) and custom validation (again through php) you could cook up just about anything.
With our global NULL argument in place, the following settings are about all we need to make this really work:
1.) Provide a default argument
2.) Argument type -> Fixed entry (Leave the default argument field blank as what gets passed is irrelevant to our needs, we simply needed to make it to the next level which is validation
3.) Choose php code as your validator
4.) Check through the $view->exposed_input array. I recommend using devel module's dsm() function here because it will respond on the ajax that view is using (unlike drupal_set_message()).
5.) Set "Action to take if argument does not validate:" to "Display empty text"
You can get as fancy in step 4 as you need, but it's just down to good old php if statements at that point.
I hope this howto helps other people. We've found it rather useful, and since it's sort of arcane, I wanted to share it.
Thanks to Earl Miles (merlinofchaos) for pointing me in the right direction on this one!
