How to pass a form field value from THEME_system_theme_settings_alter() to THEME_form_system_theme_settings_submit()

Question

MYTHEME/theme-settings.php: THEME_form_system_theme_settings_alter() builds an input form for /admin/appearance/THEME and the input (values) of the user will not be known by Drupal nor by theme_get_settings() before saving the user given input.

I'm kind of curious how to pass this value to THEME_form_system_theme_settings_submit() in theme-settings.php?

In other words: I need the value from the user input of the theme settings form BEFORE we leave theme-settings.php - Is that possible? Or do I need another way around this?

Test: Let's say the value gets stored in a 'textfield', build by the THEME_form_system_theme_settings_alter() function:

// theme-settings.php
function THEME_form_system_theme_settings_alter(&$form, &$form_state) {
// Test form      
$form['whatever_fieldset_group']['user_input'] = array(
    '#type' => 'textfield',
    '#title' => t('Test to get value'),
    '#default_value' => theme_get_setting('user_input'),
    '#description' => t('
         Type some text in textfield 
         to get shown in submit message'),
);
}

To test if I can pass that value to THEME_form_system_theme_settings_submit() we try to show the value of this field in a submit message:

// theme-settings.php
function THEME_form_system_theme_settings_submit($form, &$form_state) {

    // the following will not work inside theme-settings.php
    // because value is not known yet by theme_get_setting()
    $data = theme_get_setting('user_input');

    drupal_set_message(
          'For testing purposes we submit that you have 
           filled the textfield with the following 
           mindless value: '.$data
          );
}

This will not work. Of course. And variable_get() and variabel_set() seems to be no option ether, because we can not fill any variable without knowing the value in theme-settings.php.

The reason for asking this is, I want to write css from user input in a css file while saving theme settings. Maybe there is a way to fire a function after theme-settings got saved? Not sure. Maybe I need more examples of custom themes and how they solved it there without an additional module ...

Answer 1

The answer to the question is quite simple, but not easy to find in the d.o. docs. Thanks to Clive and Jack-PL who gave me the right direction. To reuse the example from the start question we need to summarize:

A form field input value needs to get splitt off (intercepted) from its usual way getting stored for a short moment. Why? For us to do our own processing while submission before theme-settings.php Party is over. Our form field:

// theme-settings.php
function THEME_form_system_theme_settings_alter(&$form, &$form_state) {
// Test form      
$form['whatever_fieldset_group']['user_input'] = array(
    '#type' => 'textfield',
    '#title' => t('Test to get value'),
    '#default_value' => theme_get_setting('user_input'),
    '#description' => t('
         Type some text in textfield 
         to get shown in submit message'),
);
}

Now the value will get stored when the user hits submit button. But what if we need to get in between before?

Injecting ...

drupal_set_message('<pre>' . print_r($form_state['input'],1));

... in function THEME_form_system_theme_settings_submit for a moment has revealed, that we were looking for $form_state['input']['user_input'], were our fruits are hanging. Searching the value with drupal_set_message('<pre>' . print_r($form_state['input'],1)); gives us orientation to be able to intercept the right value for our own value processing, demonstrated here in a simple representational form with another little drupal_set_message() scenario:

// theme-settings.php
function THEME_form_system_theme_settings_submit($form, &$form_state) {

    // the following will not work inside theme-settings.php
    // because value is not known yet by theme_get_setting()
    // $data = theme_get_setting('user_input');

    // But this works!
    $data = $form_state['input']['user_input'];

    drupal_set_message(
          'For testing purposes we submit that you have 
           filled the textfield with the following 
           mindless value: '. $data
          );
}

In my case, I was able to save user input into a file now with file_unmanaged_save_data($form_state['input']['user_input'],$filepath); while the user hits submit.

Thanks to Clive and Jack-PL for the fast reply. It helped me a lot!