can-access-invoice.php

<?
/**
 * Determine if user can access invoice.
 * @param WP_Post $invoice
 *   The invoice to check.
 * @return boolean
 *   TRUE if user can access invoice.
 */
function can_access_invoice ($invoice) {
  global $current_user;
  if ($current_user->can_edit("posts")) {
    return TRUE;
  }
  $classifications = wp_get_metadata(…);
  if (!empty($classifications) && in_array($classifications, $user->classification)) {
    return TRUE;
  }
  $email = wp_get_metadata(…);
  if (!empty($email) && $email == $current_user->email) {
    return TRUE;
  }
  return FALSE;
}