action is not called after a php request

I want to send a download link to user by mailchimp, after they filled out a email form.

The PHP Request listener is calling my_function(), but inside this function the action is not called.

The functions and the action are working. Also after put the do_action(); inside the createDownloadButton() it will be called. Only after write the action inside my_function() it doesn't work?!

Inside the functions.php:

        /**
        * Place a button
        * @return string html-form
        * usage: [download_button download_name='my_download']
        */    
        function createDownloadButton($atts ){
          //shortcode input
          $a = shortcode_atts( array(
              'download_name' = ''
          ), $atts );


            $result = 'form class="form" method="post" action="' . esc_url( $_SERVER['REQUEST_URI'] ) . '"';
              $result .= 'input hidden name="title" value="'.$a['download_name'].'"  type="text" '; 

              $result .= 'p';
               $result .= 'input autofocus class="imput_mail" name="email" placeholder="email adress*" value="" type="email" required'; 
               $result .= 'input class="bt" id="btn" onClick="ga(\'send\', \'event\', \'push_button\', \'some_analytics_event\');" value="" type="submit"';
              $result .= '/p';


          $result .= '/form';
          return $result;
        }
        add shortcode('download_button', 'createDownloadButton' );



    /**
    *  PHP request listener
    */
    if( isset($_POST['email'])  isset($_POST['title']) ){
       my_function($_POST['email'],$_POST['title']);
    }


    /**
    *  Do some action here
    */
    function my_function($mail, $title){
     //echo works!
     echo "scriptconsole.log( 'email: ".$mail." | download: ".$title."' );/script"; 
     //why the action doen't work here?
     do_action('memberToMailchimpList', 'API-KEY', $mail, 'LIST-ID', 'INTEREST'); 
    }