Category select function within page builder post loop

Hi,

I’ve been working with a page builder plugin from site origin which is capable of listing a post loop (via widget) and arranging the posts in order of date, post ID, comment count and others but it does not list Post by Category.

I’ve been trying to add this functionality but my PHP and wordpress skills aren’t strong enough. Are there any WP hero’s about who would find this easy to do and help me achieve this category specific listing of the post loop?

I’ve included the code from the plugin which enables the post loop widget – which is missing the category select. Its a fairly long script as its showing all of the other options included in the post loop function.

Many many thanks to anybody that replies!

class SiteOrigin_Panels_Widgets_PostLoop extends WP_Widget{
	function __construct() {
		parent::__construct(
			'siteorigin-panels-postloop',
			__( 'Blog Posts', 'so-panels' ),
			array(
				'description' => __( 'Displays a post loop.', 'so-panels' ),
			)
		);
	}

	function widget( $args, $instance ) {
		if(empty($instance['template'])) return;

		$template = $instance['template'];
		$query_args = $instance;
		unset($query_args['template']);
		unset($query_args['additional']);
		unset($query_args['sticky']);

		$query_args = wp_parse_args($instance['additional'], $query_args);

		global $wp_query;
		$query_args['paged'] = $wp_query->get('paged');

		switch($instance['sticky']){
			case 'ignore' :
				$query_args['ignore_sticky_posts'] = 1;
				break;
			case 'only' :
				$query_args['post__in'] = get_option( 'sticky_posts' );
				break;
			case 'exclude' :
				$query_args['post__not_in'] = get_option( 'sticky_posts' );
				break;
		}

		if ( !empty( $instance['title'] ) ) {
			echo $args['before_title'] . esc_html( $instance['title'] ) . $args['after_title'];
		}

		// Create the query
		query_posts($query_args);

		echo $args['before_widget'];
		locate_template($instance['template'], true, false);
		echo $args['after_widget'];

		// Reset everything
		wp_reset_query();
		wp_reset_postdata();
	}

	function update($new, $old){
		return $new;
	}

	function get_loop_templates(){
		$templates = array();

		$files = glob(get_template_directory().'/columns*.php');
		foreach($files as $file){
			$templates[] = basename($file);
		}
		$files = glob(get_stylesheet_directory().'/columns*.php');
		foreach($files as $file){
			$templates[] = basename($file);
		}
		$templates = array_unique($templates);
		sort($templates);

		return $templates;
	}

	function form( $instance ) {
		$instance = wp_parse_args($instance, array(
			'title' => '',
			'template' => 'loop.php',

			// Query args
			'post_type' => 'post',
			'posts_per_page' => '',
			'order' => 'DESC',
			'orderby' => 'date',

			'taxonomy'                 => 'category', // I've added this?!? thats my entire contribution here. 

			'sticky' => '',
			'additional' => '',
		));

		$templates = $this->get_loop_templates();
		if(empty($templates)) {
			?><p><?php _e("----", 'so-panels') ?></p><?php
			return;
		}

		// Get all the loop template files
		$post_types = get_post_types(array('public' => true));
		$post_types = array_values($post_types);
		$post_types = array_diff($post_types, array('attachment', 'revision', 'nav_menu_item'));

		?>
		<p>
			<label for="<?php echo $this->get_field_id( 'title' ) ?>"><?php _e( 'Title', 'so-panels' ) ?></label>
			<input class="widefat" name="<?php echo $this->get_field_name( 'title' ) ?>" id="<?php echo $this->get_field_id( 'title' ) ?>" value="<?php echo esc_attr( $instance['title'] ) ?>">
		</p>
		<p>
			<label for="<?php echo $this->get_field_id('template') ?>"><?php _e('Template', 'so-panels') ?></label>
			<select id="<?php echo $this->get_field_id( 'template' ) ?>" name="<?php echo $this->get_field_name( 'template' ) ?>">
				<?php foreach($templates as $template) : ?>
					<option value="<?php echo esc_attr($template) ?>" <?php selected($instance['template'], $template) ?>><?php echo esc_html($template) ?></option>
				<?php endforeach; ?>
			</select>
		</p>
		<p>
			<label for="<?php echo $this->get_field_id('post_type') ?>"><?php _e('Post Type', 'so-panels') ?></label>
			<select id="<?php echo $this->get_field_id( 'post_type' ) ?>" name="<?php echo $this->get_field_name( 'post_type' ) ?>" value="<?php echo esc_attr($instance['post_type']) ?>">
				<?php foreach($post_types as $type) : ?>
					<option value="<?php echo esc_attr($type) ?>" <?php selected($instance['post_type'], $type) ?>><?php echo esc_html($type) ?></option>
				<?php endforeach; ?>
			</select>
		</p>

		<p>
			<label for="<?php echo $this->get_field_id('posts_per_page') ?>"><?php _e('Posts Per Page', 'so-panels') ?></label>
			<input type="text" class="small-text" id="<?php echo $this->get_field_id( 'posts_per_page' ) ?>" name="<?php echo $this->get_field_name( 'posts_per_page' ) ?>" value="<?php echo esc_attr($instance['posts_per_page']) ?>" />
		</p>

		<p>
			<label <?php echo $this->get_field_id('orderby') ?>><?php _e('Order By', 'so-panels') ?></label>
			<select id="<?php echo $this->get_field_id( 'orderby' ) ?>" name="<?php echo $this->get_field_name( 'orderby' ) ?>" value="<?php echo esc_attr($instance['orderby']) ?>">
				<option value="none" <?php selected($instance['orderby'], 'none') ?>><?php esc_html_e('None', 'so-panels') ?></option>
				<option value="ID" <?php selected($instance['orderby'], 'ID') ?>><?php esc_html_e('Post ID', 'so-panels') ?></option>
				<option value="author" <?php selected($instance['orderby'], 'author') ?>><?php esc_html_e('Author', 'so-panels') ?></option>
				<option value="name" <?php selected($instance['orderby'], 'name') ?>><?php esc_html_e('Name', 'so-panels') ?></option>
				<option value="name" <?php selected($instance['orderby'], 'name') ?>><?php esc_html_e('Name', 'so-panels') ?></option>
				<option value="date" <?php selected($instance['orderby'], 'date') ?>><?php esc_html_e('Date', 'so-panels') ?></option>
				<option value="modified" <?php selected($instance['orderby'], 'modified') ?>><?php esc_html_e('Modified', 'so-panels') ?></option>
				<option value="parent" <?php selected($instance['orderby'], 'parent') ?>><?php esc_html_e('Parent', 'so-panels') ?></option>
				<option value="rand" <?php selected($instance['orderby'], 'rand') ?>><?php esc_html_e('Random', 'so-panels') ?></option>
				<option value="comment_count" <?php selected($instance['orderby'], 'comment_count') ?>><?php esc_html_e('Comment Count', 'so-panels') ?></option>
				<option value="menu_order" <?php selected($instance['orderby'], 'menu_order') ?>><?php esc_html_e('Menu Order', 'so-panels') ?></option>
				<option value="menu_order" <?php selected($instance['orderby'], 'menu_order') ?>><?php esc_html_e('Menu Order', 'so-panels') ?></option>
			</select>
		</p>

		<p>
			<label for="<?php echo $this->get_field_id('order') ?>"><?php _e('Order', 'so-panels') ?></label>
			<select id="<?php echo $this->get_field_id( 'order' ) ?>" name="<?php echo $this->get_field_name( 'order' ) ?>" value="<?php echo esc_attr($instance['order']) ?>">
				<option value="DESC" <?php selected($instance['order'], 'DESC') ?>><?php esc_html_e('Descending', 'so-panels') ?></option>
				<option value="ASC" <?php selected($instance['order'], 'ASC') ?>><?php esc_html_e('Ascending', 'so-panels') ?></option>
			</select>
		</p>

		<p>
			<label for="<?php echo $this->get_field_id('sticky') ?>"><?php _e('Sticky Posts', 'so-panels') ?></label>
			<select id="<?php echo $this->get_field_id( 'sticky' ) ?>" name="<?php echo $this->get_field_name( 'sticky' ) ?>" value="<?php echo esc_attr($instance['sticky']) ?>">
				<option value="" <?php selected($instance['sticky'], '') ?>><?php esc_html_e('Default', 'so-panels') ?></option>
				<option value="ignore" <?php selected($instance['sticky'], 'ignore') ?>><?php esc_html_e('Ignore Sticky', 'so-panels') ?></option>
				<option value="exclude" <?php selected($instance['sticky'], 'exclude') ?>><?php esc_html_e('Exclude Sticky', 'so-panels') ?></option>
				<option value="only" <?php selected($instance['sticky'], 'only') ?>><?php esc_html_e('Only Sticky', 'so-panels') ?></option>
			</select>
		</p>

		<p>
			<label for="<?php echo $this->get_field_id('additional') ?>"><?php _e('Additional ', 'so-panels') ?></label>
			<input type="text" class="widefat" id="<?php echo $this->get_field_id( 'additional' ) ?>" name="<?php echo $this->get_field_name( 'additional' ) ?>" value="<?php echo esc_attr($instance['additional']) ?>" />
			<small><?php printf(__('Additional query arguments. See <a href="%s" target="_blank">query_posts</a>.', 'so-panels'), 'http://codex.wordpress.org/Function_Reference/query_posts') ?></small>
		</p>
	<?php
	}
}