if (get_field('server_1')) {
?>
<button class="button" type="button" onClick="document.getElementById('frame').src='<?php the_field('server_1'); ?>'">Openload</button>
<center><iframe name="frame" id="frame" src="<?php the_field('server_1'); ?>" width="640" height="360" scrolling="no" frameborder="0"></iframe></center>
<?php
}