Customize the number of posts per page in SearchWP results

gistfile1.php

<?php
 
function my_searchwp_posts_per_page( $posts_per_page, $engine, $terms, $page )
{
  if( $engine != 'default' ) {
    // if this is a supplemental search engine, show 20 results per page
    return 20;
  } else {
    // it's the default search engine, return whatever it was originally
    return $posts_per_page;
  }
}
 
add_filter( 'searchwp_posts_per_page', 'my_searchwp_posts_per_page', 30, 4 );