WordPress Theme: replace logo image with title site if file doesn´t exist on server

Solved with:

<?php if (file_exists(get_template_directory().'/images/logos/'.$server_name = preg_replace('/[wW]{3,3}\.|\.(es|com|net)/', '',$_SERVER['HTTP_HOST']).'.png')) { ?>
   <a href="https://wordpress.stackexchange.com/questions/149864/<?php echo home_url("https://wordpress.stackexchange.com/" ); ?>"><img src="<?php bloginfo('stylesheet_directory'); ?>/images/logos/<?php echo $server_name = preg_replace('/[wW]{3,3}\.|\.(es|com|net)/', '',$_SERVER['HTTP_HOST']).'.png' ?>" border="0" width="230px" height="60px" alt="<?php bloginfo( 'name' ); ?>"/></a>
  <?php  }else{ ?>
<h3><?php bloginfo( 'name' ); ?></h3>
  <?php } ?>

Thanks at all!