<?php
$posts = R::findOne('posts');
echo $posts->$id, '<br>';
echo $posts->head, '<br>';
echo $posts->desc;
?> $posts = R::findAll('posts');. Затем в цикле выводите записи.
<?php
$id = []
$id[] = '1';
$id[] = '2';
$id[] = '3';
$id[] = '4';
$posts = R::findOne('posts', 'id', $id );
echo $posts->head, '<br>';
echo $posts->desc;<?php
$posts = R::findOne('posts', 'id', [ '1', '2', '3', '4' ] );
или
$posts = R::findOne('posts', 'id', [ 1, 2, 3, 4 ] );
echo $posts->head, '<br>';
echo $posts->desc;