
<?php

global $posts;
$posts = array( 1, 2, 3, 4, 5 );
$args = array(
    'post__in'             => $posts,
    'posts_per_page'   => 5, 
    'caller_get_posts'  => 1 // ignore sticky status
);
$my_query = new WP_Query( $args );
/**
 * Order an array of objects by object property
 */
function orderby( $a, $b ) {
    global $posts;
    $apos   = array_search( $a->ID, $posts );
    $bpos   = array_search( $b->ID, $posts );
    return ( $apos < $bpos ) ? -1 : 1;
}
usort( $my_query->posts, "orderby" );
?>