WordPress RSS小工具详解

我们可以通过RSS来订阅别人的网站内容，例如WordPress头条的Feed地址是http://www.wptoutiao.com/feed，WordPress提供了一个RSS小工具，可以在侧边栏展示网站的Feed内容。今天就来详细介绍一下WordPress RSS小工具。

WordPress RSS小工具使用介绍

在网站【后台-外观-小工具】中找到RSS小工具，将它拖到想要展示的侧边栏中。

设置选项：
1.RSS Feed地址（例：http://www.wptoutiao.com/feed）
2.Feed的标题设置
3.Feed内容数量
4.是否显示条目内容
5.是否显示条目作者
6.是否显示条目日期
设置完成保存就可以了。

WordPress RSS小工具源码介绍

源码位置：wp-includes\widgets\class-wp-widget-rss.php
源代码：(since 4.4.0)

 __( 'Entries from any RSS or Atom feed.' ),
			'customize_selective_refresh' => true,
		);
		$control_ops = array( 'width' => 400, 'height' => 200 );
		parent::__construct( 'rss', __( 'RSS' ), $widget_ops, $control_ops );
	}

	/**
	 * Outputs the content for the current RSS widget instance.
	 *
	 * @since 2.8.0
	 * @access public
	 *
	 * @param array $args     Display arguments including 'before_title', 'after_title',
	 *                        'before_widget', and 'after_widget'.
	 * @param array $instance Settings for the current RSS widget instance.
	 */
	public function widget( $args, $instance ) {
		if ( isset($instance['error']) && $instance['error'] )
			return;

		$url = ! empty( $instance['url'] ) ? $instance['url'] : '';
		while ( stristr($url, 'http') != $url )
			$url = substr($url, 1);

		if ( empty($url) )
			return;

		// self-url destruction sequence
		if ( in_array( untrailingslashit( $url ), array( site_url(), home_url() ) ) )
			return;

		$rss = fetch_feed($url);
		$title = $instance['title'];
		$desc = '';
		$link = '';

		if ( ! is_wp_error($rss) ) {
			$desc = esc_attr(strip_tags(@html_entity_decode($rss->get_description(), ENT_QUOTES, get_option('blog_charset'))));
			if ( empty($title) )
				$title = strip_tags( $rss->get_title() );
			$link = strip_tags( $rss->get_permalink() );
			while ( stristr($link, 'http') != $link )
				$link = substr($link, 1);
		}

		if ( empty($title) )
			$title = empty($desc) ? __('Unknown Feed') : $desc;

		/** This filter is documented in wp-includes/widgets/class-wp-widget-pages.php */
		$title = apply_filters( 'widget_title', $title, $instance, $this->id_base );

		$url = strip_tags( $url );
		$icon = includes_url( 'images/rss.png' );
		if ( $title )
			$title = ' '. esc_html( $title ) . '';

		echo $args['before_widget'];
		if ( $title ) {
			echo $args['before_title'] . $title . $args['after_title'];
		}
		wp_widget_rss_output( $rss, $instance );
		echo $args['after_widget'];

		if ( ! is_wp_error($rss) )
			$rss->__destruct();
		unset($rss);
	}

	/**
	 * Handles updating settings for the current RSS widget instance.
	 *
	 * @since 2.8.0
	 * @access public
	 *
	 * @param array $new_instance New settings for this instance as input by the user via
	 *                            WP_Widget::form().
	 * @param array $old_instance Old settings for this instance.
	 * @return array Updated settings to save.
	 */
	public function update( $new_instance, $old_instance ) {
		$testurl = ( isset( $new_instance['url'] ) && ( !isset( $old_instance['url'] ) || ( $new_instance['url'] != $old_instance['url'] ) ) );
		return wp_widget_rss_process( $new_instance, $testurl );
	}

	/**
	 * Outputs the settings form for the RSS widget.
	 *
	 * @since 2.8.0
	 * @access public
	 *
	 * @param array $instance Current settings.
	 */
	public function form( $instance ) {
		if ( empty( $instance ) ) {
			$instance = array( 'title' => '', 'url' => '', 'items' => 10, 'error' => false, 'show_summary' => 0, 'show_author' => 0, 'show_date' => 0 );
		}
		$instance['number'] = $this->number;

		wp_widget_rss_form( $instance );
	}
}

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