Settings API - getting hidden input / submit button's name

Question

I'm generating this form using Settings API:

<form action="options.php" method="post">   
   <?php settings_fields('XX_theme_settings'); do_settings_sections('my_settings'); ?>
   <input type="hidden" name="foo" value="bar" />
   <input name="SubmitButton" type="submit" class="button-primary" value="<?php _e('Save Changes'); ?>" />   
</form>

Validation callbacks $input array returns only 'my_settings' input fields.

How do I access foo (bar) input's value and submit button's name SubmitButton?

This doesn't work for the hidden input:

my_validation($input) {
   $foo = $input['foo'];
}

And when it comes to the submit button I don't even know where to start.

Answer 1

Using $_POST is too low level. Simply give it the same name as your other options. When you options are displayed they should have the names of the form: my_settings[a_particular_option]. For instance:

<input name="my_settings[some_input_option]"/>

Then for your hidden input and submit button:

<input type="hiddden" name="my_settings[foo]" value="bar"/>
<input name="my_settings[SubmitButton]" type="submit" class="button-primary" value="<?php _e('Save Changes'); ?>"/>

In your validation array

my_validation($input) {
   $foo = $input['foo'];
   $submit = $input['SubmitButton'];
}