Şu şekilde dener misiniz ?
<?php
$thh=mysql_query("select p_id from fmd_encok where p_id='19' desc limit ".fmd_sabit("1"));
while($g=mysql_fetch_object($thh))$ref[]=$g->p_id;
$args = array( 'post__in' => $ref );
$posts_array = get_posts( $args );
foreach ($posts_array as $post) : setup_postdata($post);
?>
: mysql_fetch_object(): supplied argument is not a valid MySQL result resource in
olmadı hocam. hatasını verdi hocam.