[WordPress][Plugin] 外部サイトをクロールして、特定の要素を XPath で切り出して表示するウィジェット

remote-site-parts.php

<?php
/**
 * Adds Remote_Site_Parts widget.
 */
add_action( 'widgets_init', function(){
	register_widget( 'Remote_Site_Parts' );
});
class Remote_Site_Parts extends WP_Widget {
	private $options = [
		'title' => 'Title:',
		'url' => 'URL:',
		'xpath_query' => 'XPATH:',
		'expiration' => 'Expiration:',
		'user_agent' => 'User-Agent (option):',
		'user' => 'BASIC Auth User (option):',
		'password' => 'BASIC Auth Password (option):',
	];
	private $transient_key;
	const DEFAULT_EXPIRATION = 60 * MINUTE_IN_SECONDS;

	/**
	 * Register widget with WordPress.
	 */
	function __construct() {
		parent::__construct(
			'remote_site_parts', // Base ID
			'Remote site parts' // Name
		);
		$this->transient_key = $this->get_field_id( 'transients' );
	}

	/**
	 * Outputs the options form on admin
	 *
	 * @see WP_Widget::form()
	 *
	 * @param array $instance The widget options
	 */
	public function form( $instance ) {
		echo "<p>\n";
		foreach ( $this->options as $key => $lavel ) {
			$value = (! empty( $instance[$key] )) ? $instance[$key] : '';
			if ( $key === 'expiration' ) {
				$value = intval( isset( $instance[$key] ) ? $instance[$key] : self::DEFAULT_EXPIRATION );
			}
			printf(
				'<label for="%s">%s</label>',
				$this->get_field_id( $key ),
				$lavel
			);
			printf(
				'<input class="widefat" id="%s" name="%s" type="text" value="%s">',
				$this->get_field_id( $key ),
				$this->get_field_name( $key ),
				esc_attr( $value )
			);
			echo "\n";
		}
		echo "</p>\n";
	}

	/**
	 * Sanitize widget form values as they are saved.
	 *
	 * @see WP_Widget::update()
	 *
	 * @param array $new_instance Values just sent to be saved.
	 * @param array $old_instance Previously saved values from database.
	 *
	 * @return array Updated safe values to be saved.
	 */
	public function update( $new_instance, $old_instance ) {
		$instance = array();
		foreach ( $this->options as $key => $lavel ) {
			if ( $key === 'expiration' ) {
				$value = intval( isset( $new_instance[$key] ) ? $new_instance[$key] : self::DEFAULT_EXPIRATION );
			} else {
				$value = sanitize_text_field( isset( $new_instance[$key] ) ? $new_instance[$key] : '' );
			}
			$instance[$key] = $value;
		}
		delete_transient( $this->transient_key );
		return $instance;
	}

	/**
	 * Front-end display of widget.
	 *
	 * @see WP_Widget::widget()
	 *
	 * @param array $args     Widget arguments.
	 * @param array $instance Saved values from database.
	 */
	public function widget( $args, $instance ) {
		$defaults = [
			'expiration' => self::DEFAULT_EXPIRATION
		];
		$instance = wp_parse_args((array) $instance, $defaults );
		if ( empty( $instance['url'] ) || empty( $instance['xpath_query'] ) ) {
			return;
		}

		if ( false === ( $output_html = get_transient( $this->transient_key ) ) ) {
			$output_html = '';
			$remote_get_args = [];
			if ( ! empty( $instance['user'] ) && ! empty( $instance['password'] ) ) {
				$remote_get_args['headers'] = [
					'Authorization' => 'Basic '.base64_encode( "{$instance['user']}:{$instance['password']}" ),
				];
			}
			if ( ! empty( $instance['user_agent'] ) ) {
				$remote_get_args['user-agent'] = $instance['user_agent'];
			}
			$response = wp_remote_get( $instance['url'], $remote_get_args );
			if ( ! is_wp_error( $response ) && wp_remote_retrieve_response_code( $response ) == 200 ) {
				$html = wp_remote_retrieve_body( $response );
				$dom = new DOMDocument;
				@$dom->loadHTML( $html );
				$xpath = new DOMXPath( $dom );
				foreach ( $xpath->query( $instance['xpath_query'] ) as $node ) {
					$output_html .= $this->getInnerHtml( $node );
				}
				unset( $dom );
				unset( $xpath );
				set_transient( $this->transient_key, $output_html, intval( $instance['expiration'] ) );
			}
			unset( $remote_get_args );
			unset( $response );
		}
		echo isset($args['before_widget']) ? $args['before_widget'] : '';
		echo $output_html;
		echo isset($args['after_widget']) ? $args['after_widget'] : '';
	}

	/**
	 * 
	 *
	 * @param array $node     object
	 */
	private function getInnerHtml($node){
		$children = $node->childNodes;
		$html = '';
		foreach( $children as $child ){
			$html .= $node->ownerDocument->saveHTML( $child );
		}
		unset( $children );
		return $html;
	}
} // class Remote_Site_Parts