How elaborate input of a WordPress shortcode form ($_POST array)?

Question

I'm trying to create a custom WordPress shortcode to generate a form. I wrote a function ( called send_advice_request_form() ) that returns HTML form code, then the callback that use ob_start() and return ob_get_clean(), how can I elaborate submitted form data? If I don't indicate any action attribute for form, where the post data will be submitted?

function send_advice_request_form_cb() {

    ob_start();

    echo send_advice_request_form();

    return ob_get_clean();

}
add_shortcode( 'dparequestform', 'send_advice_request_form_cb' );

function send_advice_request_form() { //return HTML form }

Answer 1

The best way for handling custom form like yours is to send the datas to admin-post.php

Create a form with this action and this input type hidden :

<form action="<?php echo esc_url(admin_url('admin-post.php')); ?>">
  /*
     Your fields here.
  */

   <input type="hidden" name="action" value="your_action_name">
</form>

Then you will have to handle datas with those hooks

function send_advice_request_handler() {

    /*
       Do what you have to do.
    */
}

// Hook for everyone, no private
add_action( 'admin_post_nopriv_your_action_name', 'send_advice_request_handler' );

// Hook only for logged in users (verified by wordpress with is_user_logged_in())
add_action( 'admin_post_contact_form', 'send_advice_request_handler' );

I hove it will helps you, tell me if you need more help.