<?php
// Variables could be data pulled from DB as well

$some_stuff = $wpdb->(...)
$my_classes = array(...);

foreach ($my_classes as $my_class) :

  eval('
    class ' . $my_class . ' extends WP_Widget {
      // Extra stuff here using $my_class or $some_stuff variable
    }
  ');

// after eval() register each widget

endforeach;