[WordPress]wp_queryで最新投稿10件の中からランダム5件表示

<?php
$args = array(
    'posts_per_page'   => 10
);
$posts_array = get_posts( $args );
foreach ( $posts_array as $post ) : setup_postdata( $post );
    $post_id = $post->ID;
    $id_array[] = $post->ID;
endforeach;
wp_reset_postdata();

$args = array(
    'post__in' => $id_array,
    'orderby' => 'rand',
    'posts_per_page' => '5',
);
$query = new WP_Query( $args );
while ( $query->have_posts() ) {
$query->the_post();
    echo '<p>' . get_the_title() . '</p>';
}
wp_reset_postdata();
?>