How to adapt the source code of the module to the native file show.full.php cms DLE?

Question

DLE

There is a module that I found on the pages of the site.

$xflist = dle_cache( $xfname, $config['skin'] );
if(!$xflist) {
  $sql_result = $db->query( "SELECT xfields FROM " . PREFIX . "_post WHERE approve=1" );
  while ( $rows = $db->get_row( $sql_result ) ) {
    $xfields[] = $rows;
  }
  $stack = array();
  foreach($xfields as $value){
    if($value[xfields]){
      $row = xfieldsdataload($value[xfields]);
      if($row[$xfname]){
        $rowdata = explode( "~", $row[$xfname]);
        foreach($rowdata as $value){
          if($value){
            $value = trim($value);
            array_unshift($stack, $value);
          }
        }
      }
    }
  }
  sort ($stack);	
  $stack = array_count_values( $stack );
  foreach( $stack as $value => $count ){
    $xflist .= "<option value=" . $value . " data-subtext=" .$count . ">" . $value ."</option>";
  }
  create_cache( $xfname, $xflist, $config['skin'] );
}
echo $xflist;

It displays all involved additional fields in a list under select (if I understand correctly).
But it only works through an include connection.
How to remake it correctly so that it can be inserted into show.full.php and display all the news with the value of a certain additional field in some {item-news} tag, for example?