There is a lot of stuff going on there. I made my own example to test. I can reproduce the issue. It appears to me that CF7 is not recognizing the SELECT’s NAME attribute.
Ignoring CFDB for a moment, if I set the custom tag in the CF7 email template, I can see that it does not get populated in the email, implying that CF7 is not processing it. As a general rule, if you can’t get it to show in the CF7 email, then CFDB cannot see it also. Therefore it is an issue inside CF7.
The workaround I found was to set the NAME in the code that generates the select instead of in the CF7 custom shortcode.
Specifically for you change:
$output = "<select id='corsi'>";
to
$output = "<select id='corsi' name='corsi'>";
This means that [corsidropdown corsi] should just be [corsidropdown] and
wpcf7_add_shortcode('corsidropdown', 'createbox', true);
should just be:
wpcf7_add_shortcode('corsidropdown', 'createbox');
Here is a more simple test case. You should pass this on to the CF7 forum:
This does NOT work:
CF7 Form definition:
<p> Your Car [carselect car] </p> <!-- name "car" provided -->
<p>[submit "Send"]</p>
Registering custom short code:
add_action('wpcf7_init', 'add_cf7_carselect_shortcode');
function add_cf7_carselect_shortcode() {
wpcf7_add_shortcode('carselect', 'cf7_car_select', true);
}
function cf7_car_select() {
// NOT setting "name" below
return '<select id="car">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</select>';
}
But this DOES work
CF7 Form definition:
<p> Your Car [carselect] </p> <!-- no name -->
<p>[submit "Send"]</p>
Registering custom short code:
add_action('wpcf7_init', 'add_cf7_carselect_shortcode');
function add_cf7_carselect_shortcode() {
//wpcf7_add_shortcode('carselect', 'cf7_car_select', true);
wpcf7_add_shortcode('carselect', 'cf7_car_select');
}
function cf7_car_select() {
// Explicitly setting "name" below
return '<select name="car" id="car">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</select>';
}
