Views: Searching multiple fields with one exposed filter

Here's a nice little gem i've learned today.
I needed to have one exposed filter search on multiple fields in views.

Here's one way to get this working.

Let's say we have 3 CCK text fields we want to search on: first name, last name and location.
What we need, is be able to make an 'OR statement' between the different views filters.
For this, i used the 'views OR' module.

We setup an OR statement by adding a 'views OR: Begin alternatives' filter, which you can find under the 'views or' group.

Next, add the first cck filter, expose it, and set it to 'contains' for searching.
Do this for all the other fields, but between each field, you add a 'Views Or: Next alternative' filter between them, and a 'Views Or: End alternatives' after the last filter you want to share.

So you should have something like this:

Views Or: Begin alternatives =
Content: Firstname exposed
Views Or: Next alternative =
Content: Lastname exposed
Views Or: Next alternative =
Content: Location exposed
Views Or: End alternatives =

Now we need to export our view so we can make a module of it with hook_views_default_views(), have a look at this article on how to do this.
Once you have your view exported to a module, look for your your exposed filters in the code and change the 'identifier' to 'search' for example. Do this for the 3 filters.
It is important that they have the same identifier, otherwise it won't work.

  'field_firstname_value' => array(
    'operator' => 'contains',
    'value' => '',
    'group' => '0',
    'exposed' => TRUE,
    'expose' => array(
      'use_operator' => 0,
      'operator' => 'field_firstname_value_op',
      'identifier' => 'field_firstname_value', // <== change this value
      'label' => 'Firstname',
      'optional' => 1,
      'remember' => 0,
    ),

Save your module, enable it, and flush views caches at views tools.
(admin/build/views/tools)
If everything went fine, you should now be able to share multiple exposed filters.

One more thing, we still see the other filters, or even only the filter labels.
We can unset them with another views hook, hook_form_views_exposed_form_alter().

Have a look at following example to unset the other fields.

function custommodule_form_views_exposed_form_alter(&$form, $form_state) {
  switch ($form_state['view']->name) {
    case 'customview':
      unset($form['#info']['filter-field_lastname_value']);
      unset($form['#info']['filter-field_location_value']);
      $form['submit']['#value'] = t('Search');
      break;
  }
}

Of course, your module, views and field names will be different, so don't forget to change them. ;)
Voila, one exposed filter field, searching within multiple shared fields.

Thanks to the excellent comment by jpklein, and mzenner for the tip.