Conditional Custom field with foreach

Question

i use use this code to set slider in header with CF, how i can disable when CF is empty or set another CF key to exclude it?

<?php
  $custom_fields = get_post_custom($post_id);//Current post id
  $my_custom_field = $custom_fields['slider_id'];//key name
  foreach ( $my_custom_field as $key => $value )
  echo get_new_royalslider($value) ;
?>

Answer 1

Less code lines with get_post_custom_values()

$values = get_post_custom_values('slider_id', $post_id);

// if non-empty
if($values) {
    foreach($values as $value)
        echo get_new_royalslider($value);
}

If $values array is empty, nothing happens.