$args = array( 'numberposts' => 5, 'orderby' => 'rand', 'post_status' => 'publish' );
$rand_posts = get_posts( $args );

<ul>
<?php
$args = array( 'numberposts' => 5, 'orderby' => 'rand', 'post_status' => 'publish' );
$rand_posts = get_posts( $args );
foreach( $rand_posts as $post ) : ?><li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
<?php endforeach; ?>
</ul>

/*** Random_Posts widget class** Author: haoxian_zeng <http://cnzhx.net/>* Date: 2013.05.14, cnzhx2011 1.0*/
//--------------- * 注册该微件
class WP_Widget_myRandom_Posts extends WP_Widget {function __construct() {$widget_ops = array('classname' => 'widget_my_random_posts', 'description' => __( '水景一页定制的随机文章微件。The cnzhx customized random posts widget.' ) );parent::__construct('random-posts', __('随机文章 Random Posts'), $widget_ops);$this->alt_option_name = 'widget_my_random_posts';}function widget( $args, $instance ) {global $randomposts, $post;extract($args, EXTR_SKIP);$output = '';// 设置 widget 标题$title = apply_filters('widget_title', empty($instance['title']) ? __('随机文章 Random Posts') : $instance['title']);// 设置要获取的文章数目if ( ! $number = absint( $instance['number'] ) )$number = 5;// WP 数据库查询，使用 rand 参数来获取随机的排序，并取用前面的 $number 个文章$randomposts = get_posts( array( 'number' => $number, 'orderby' => 'rand', 'post_status' => 'publish' ) );// 下面开始准备输出数据// 先输出一般的 widget 前缀$output .= $before_widget;// 输出标题if ( $title )$output .= $before_title . $title . $after_title;// random posts 列表开始$output .= '<ul id="randomposts">';if ( $randomposts ) {foreach ( (array) $randomposts as $post) {$output .= '<li><a href="' . get_permalink() . '">' . $post->post_title . '</a></li>';}}$output .= '</ul>';// 输出一般的 widget 后缀$output .= $after_widget;// 输出到页面echo $output;}function update( $new_instance, $old_instance ) {$instance = $old_instance;$instance['title'] = strip_tags($new_instance['title']);$instance['number'] = absint( $new_instance['number'] );$alloptions = wp_cache_get( 'alloptions', 'options' );if ( isset($alloptions['widget_my_random_posts']) )delete_option('widget_my_random_posts');return $instance;}//// 在 WP 后台的 widget 内部显示两个参数, 1. 标题；2. 显示文章数目//function form( $instance ) {$title = isset($instance['title']) ? esc_attr($instance['title']) : '';$number = isset($instance['number']) ? absint($instance['number']) : 5;?><p><label for="<?php echo $this->get_field_id('title'); ?>"><?php _e('Title:'); ?></label><input class="cnzhx" id="<?php echo $this->get_field_id('title'); ?>" name="<?php echo $this->get_field_name('title'); ?>" type="text" value="<?php echo $title; ?>" /></p><p><label for="<?php echo $this->get_field_id('number'); ?>"><?php _e('Number of posts to show:'); ?></label><input id="<?php echo $this->get_field_id('number'); ?>" name="<?php echo $this->get_field_name('number'); ?>" type="text" value="<?php echo $number; ?>" size="3" /></p><?php}
}// register WP_Widget_myRandom_Posts widget
add_action( 'widgets_init', create_function( '', 'return register_widget("WP_Widget_myRandom_Posts");' ) );