Александр

$form = $this->createForm(ConferenceType::class, $conference, array(
...

$fields = array();
				for ($i = 1; $i < 40; $i++) 
				  { 
					$fields[$i] = get_field('hotels'.$i);	
				  } 
foreach ($fields as $key  ){
    foreach ($key as $var  )
    {
		echo '<option  value="'.$var.'">'.$var.'</option>';
    }										
}