title: Modify WordPress plugin function in 'functions.php'
body: <p>I need to change the value of a function from a WordPress plugin that I'm using.</p>
  <p>If I do it in the original plugin file, it works perfectly, but I'd rather make it in file <em>functions.php</em> to avoid problems on plugin update.</p>
  <p>I need to change this:</p>
  <pre><code>public static function loop_shop_per_page() {
      return get_option( 'posts_per_page' );
  }
  </code></pre>
  <p>Into this:</p>
  <pre><code>public static function loop_shop_per_page() {
      return '-1';
  }
  </code></pre>
  <p>How would I go to create a filter in file <em>functions.php</em> to do just that?</p>