Delete ghost or dead fields in your Drupal 7 website. Sometimes you will end up with dead fields in your database after altering a feature that contained content types. This gist will get all the linked fields from your entities, all the fields defined in the database, find out the difference between them, and remove them.

gistfile1.php

  // Get all fields linked to entities.
  $active = [];
  $entities = field_info_instances('node');
  foreach ($entities as $entity) {
    foreach ($entity as $field_name => $field_info) {
      $active[] = $field_name;
    }
  }
  $active = array_unique($active);

  // Get all fields in database.
  $all = [];
  $result = db_query('SELECT field_name FROM {field_config}');
  foreach ($result as $record) {
    $all[] = $record->field_name;
  }
  $all = array_unique($all);

  // Find out the dead fields, and delete them.
  $dead = array_diff($all, $active);
  foreach ($dead as $field) {
    field_delete_field($field);
  }

  // Purge cache
  field_purge_batch(count($dead));