Widget that displays the latest WordPress posts from a certain category / Widget que mostra os últimos posts de uma determinada categoria

widget-posts-from-category.php

<?php
/**
 * Cria o Widget que mostra os posts da categoria selecionada
 *
 */
class Recent_Category_Posts extends WP_Widget {

	/**
	 * Constructor
	 *
	 * @return void
	 **/
	function Recent_Category_Posts() {
		$widget_ops = array( 'classname' => 'widget_recent_category_posts', 'description' => __( 'Displays the latest posts from a certain category', '' ) );
		$this->WP_Widget( 'widget_recent_category_posts', __( 'Recent Category Posts', '' ), $widget_ops );
		$this->alt_option_name = 'widget_recent_category_posts';

		add_action( 'save_post', array(&$this, 'flush_widget_cache' ) );
		add_action( 'deleted_post', array(&$this, 'flush_widget_cache' ) );
		add_action( 'switch_theme', array(&$this, 'flush_widget_cache' ) );
	}

	/**
	 * Outputs the HTML for this widget.
	 *
	 * @param array An array of standard parameters for widgets in this theme
	 * @param array An array of settings for this widget instance
	 * @return void Echoes it's output
	 **/
	function widget( $args, $instance ) {
		$cache = wp_cache_get( 'widget_recent_category_posts', 'widget' );

		if ( !is_array( $cache ) )
			$cache = array();

		if ( ! isset( $args['widget_id'] ) )
			$args['widget_id'] = null;

		if ( isset( $cache[$args['widget_id']] ) ) {
			echo $cache[$args['widget_id']];
			return;
		}

		ob_start();
		extract( $args, EXTR_SKIP );

		// Category ID
		$category = (int) $instance['category'];
		
		// Não havendo título, usamos o nome da categoria
		$title = apply_filters( 'widget_title', empty( $instance['title'] ) ? get_category( $category )->name : $instance['title'], $instance, $this->id_base );

		// Número de posts
		if ( ! $number = absint( $instance['number'] ) )
 			$number = 5;
		
		$category_args = array(
			'cat'					=> $category,
			'posts_per_page'		=> $number,
			'post_status' 			=> 'publish',
			'ignore_sticky_posts'	=> true
		);
		
		$category_posts = new WP_Query( $category_args );

		if ( $category_posts->have_posts() ) :
			echo $before_widget;
			
			echo $before_title;
			echo '<a href="' . get_category_link( $category ) . '" title="' . sprintf( 'View all posts filed under %s', get_category( $category )->name ) . '">' . $title . '</a>';
			echo $after_title;
			
			echo '<ul>';
			
			while ( $category_posts->have_posts() ) : $category_posts->the_post(); ?>
				<li>
					<a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a>
				</li>
			<?php
			endwhile;
			
			echo '</ul>';
			
			// Final do widget
			echo $after_widget;

			// Reinicia o postdata
			wp_reset_postdata();

		
		endif; // if ( have_posts() )

		$cache[$args['widget_id']] = ob_get_flush();
		wp_cache_set( 'widget_recent_category_posts', $cache, 'widget' );
	}

	/**
	 * Deals with the settings when they are saved by the admin. Here is
	 * where any validation should be dealt with.
	 **/
	function update( $new_instance, $old_instance ) {
		$instance = $old_instance;
		$instance['title'] = strip_tags( $new_instance['title'] );
		$instance['category'] = (int)( $new_instance['category'] );
		$instance['number'] = (int) $new_instance['number'];
		
		$this->flush_widget_cache();

		$alloptions = wp_cache_get( 'alloptions', 'options' );
		if ( isset( $alloptions['widget_recent_category_posts'] ) )
			delete_option( 'widget_recent_category_posts' );

		return $instance;
	}

	function flush_widget_cache() {
		wp_cache_delete( 'widget_recent_category_posts', 'widget' );
	}

	/**
	 * Displays the form for this widget on the Widgets page of the WP Admin area.
	 **/
	function form( $instance ) {
		$title = isset( $instance['title']) ? esc_attr( $instance['title'] ) : '';
		$category = isset( $instance['category'] ) ? (int) $instance['category'] : 0;
		$number = isset( $instance['number'] ) ? absint( $instance['number'] ) : 5;
		?>
		
		<p><label for="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>"><?php _e( 'Title:', '' ); ?></label>
		<input class="widefat" id="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'title' ) ); ?>" type="text" value="<?php echo esc_attr( $title ); ?>" /></p>

		<p><label for="<?php echo $this->get_field_id( 'category' ); ?>"><?php _e( 'Category:', '' ); ?></label>
		<?php wp_dropdown_categories( 'name='.$this->get_field_name( 'category' ) . '&id=' . $this->get_field_id( 'category' ) . '&show_count=1&class=widefat&selected=' . $category );?></p>
		
		<p><label for="<?php echo esc_attr( $this->get_field_id( 'number' ) ); ?>"><?php _e( 'Number of posts to show:', '' ); ?></label>
		<input id="<?php echo esc_attr( $this->get_field_id( 'number' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'number' ) ); ?>" type="text" value="<?php echo esc_attr( $number ); ?>" size="3" /></p>
		
	<?php
	}
}

/**
 * Registra os widgets personalizados do tema
 *
 */
function my_register_widgets() {

	register_widget( 'Recent_Category_Posts' );
	
}

add_action( 'widgets_init', 'my_register_widgets' );
?>