Kako da poslati vrednosti sa forme?

Pokušavam da vrednosti sa forme u svom plaginu pošaljem na drugi fajl u okviru istog plagina.

Ovo je code

public function widget( $args, $instance ) {
        echo $args['before_widget'];
        if ( ! empty( $instance['title'] ) ) {
            echo $args['before_title'] . apply_filters( 'widget_title', $instance['title'] ) . $args['after_title'];
        }
        ?>
 
         <form id='subscriber-form' method='post' action="<?php echo plugins_url( 'newsletter_subscriber_mailer.php', __FILE__ ); ?>" >
            <input type='text' class='form-control' id='name' name='name' placeholder='Insert your fullname' />
            <input type='text' class='form-control' id='email' name='email' placeholder='Insert your email' />
            <input type='hidden' name='recipient' id='recipient' value='<?php echo $instance['recipient'];?>'/>
            <input type='hidden' name='subject' id='subject' value='<?php echo $instance['subject'];?>' />
            <input type='submit' name='subscriber_submit' class='btn btn-primary' value='Subscribe' />
         </form>
 
        <?php
        echo $args['after_widget'];
    }

Šta je potrebno ubaciti u action kako bih to postigao?