HOw to create a unquie Header on every post

I found the following from a post 6 years ago.

<?php
if(is_single() & !is_home()) {
  $myfield = 'custom_field_name'; // Change this to the name of the custom field you use..
  $postimage = get_post_meta($post->ID, $myfield, true);
?>
  <style type="text/css">
  <!--
    .yourheaderclass {
        border:none;
        color:black;
      <?php
      if($postimage) { // If the field has a value.. set background image using value...
      ?>
        background-image: url('some/path/to/image/<?php echo $postimage; ?>.jpg');
      <?php
      } elseif(!$postimage) { // If no value
      ?>
        background-image: none;
      <?php
      }
      ?>
    }
  -->
  </style>
<?php
}
?>

I do not have ‘custom_field_name’ and am unsure if the php is still usable. Can anyone confirm if this still works or have a solution for 4.4.2.

Regards,

Matt