WordPress Shortcode Display Posts with Tax Filter

class-posts-tax-filter.php

<?php 

/**
 * Display posts with taxonomy filter
 * 
 * Add file to same folder as functions.php
 * Add to functions.php: get_template_part( 'class-posts-tax-filter', '' );
 * USAGE: [posts_tax_filter post_type="post" qty="6"]
 */

// Exit if accessed directly.
if ( !defined( 'ABSPATH' ) ) {
	exit;
}


/**
 * Initiate the class
 */
new ERI_POSTS_TAX_FILTER;


/**
 * The class.
 */
class ERI_POSTS_TAX_FILTER {

    /**
	 * Constructor
     * Add hooks like so: add_filter( 'filter_name', [$this, 'function_name' ] );
     * Run functions directly like so: $this->fake_function();
	 */
	public function __construct() {

            // Shortcode
            add_shortcode( 'posts_tax_filter', [ $this, 'shortcode' ] );

	} // End __construct()


    /**
     * The shortcode
     *
     * @return string
     */
    public function shortcode( $atts ) {
        // Get the attributes
        $atts = shortcode_atts( [ 
            'post_type' => 'post',
            'taxonomies' => '',
            'qty' => 6
        ], $atts );

        // If we have more than one post type, let's convert to array
        if ( strpos( $atts[ 'post_type' ], ',' ) !== false ) {
            $post_types = explode( ',', str_replace( ' ', '', $atts[ 'post_type' ] ) );

        // Add the single post type to an array
        } else {
            $post_types = [ $atts[ 'post_type' ] ];
        }
        
        // Iter the post types
        foreach ( $post_types as $post_type ) {

            // Get the taxonomies
            $this_taxonomies = get_object_taxonomies( $post_type );

            // Add the taxonomies
            foreach ( $this_taxonomies as $t ) {
                $taxonomies[] = $t;
            }
        }

        // Add some CSS
        $results = '<style>
        .ptf-outer-container {
            display: flex;
            justify-content: space-between; 
            align-items: stretch; 
            flex-direction: row; 
            flex-wrap: wrap; 
            align-content: flex-start;
            height: 100%;
            gap: 20px;
        }
        .ptf-outer-container .post-container {
            border: 1px solid #ddd;
            border-radius: 10px;
            box-shadow: 2px 2px 10px #ddd;
            padding: 20px;
            width: 30%;
        }
        .ptf-outer-container h4 {
            margin-top: 0;
        }
        </style>';

        // Get the current page
        $page = get_query_var( 'paged' );

        // Get the current url
        global $wp;
        $current_url =  home_url( $wp->request );
        $pos = strpos( $current_url , '/page' );
        $current_url = substr( $current_url, 0, $pos );

        // Capture the filtered terms
        if ( isset( $_GET[ 'term' ] ) && $_GET[ 'term' ] != '' ) {
            $search_term = sanitize_text_field( $_GET[ 'term' ] );
        } else {
            $search_term = false;
        }

        // Start the filter
        $results .= '<form method="get" action="'.$current_url.'">
            <label for="pft-filter"></label>
            <select id="pft-filter" name="term">
                <option>-- Select a Taxonomy Term to Filter --</option>';

                // Add the taxonomies
                foreach ( $taxonomies as $taxonomy ) {

                    // Get all terms for this taxonomy
                    $this_terms = get_terms( $taxonomy, array(
                        'hide_empty' => true,
                    ) );

                    // Get the tax object
                    $taxonomy = get_taxonomy( $taxonomy );
                    // dpr( $taxonomy );
                    
                    // Iter the terms
                    foreach ( $this_terms as $this_term ) {

                        // Mark selected
                        if ( $search_term && $this_term->term_id == $search_term ) {
                            $selected = ' selected';
                        } else {
                            $selected = '';
                        }

                        // Add the option
                        $results .= '<option value="'.$this_term->term_id.'"'.$selected.'>'.$taxonomy->labels->singular_name.': '.$this_term->name.'</option>';
                    }
                }                

            // Add the view button
            $results .= '<input type="submit" value="View" />';
        
        // End the filter
        $results .= '</select>
        </form>';

        // Start the query args
        $args = [
            'post_type' => $post_types,
            'posts_per_page' => $atts[ 'qty' ],
            'paged' => $page
        ];

        // Are we filtering by tax?
        if ( $search_term ) {

            // Get the tax
            $this_term = get_term( $search_term );

            // Start the tax query
            $tax_query = [
                'taxonomy' => $this_term->taxonomy,
                'field' => 'term_id',
                'terms' => $search_term
            ];

            // Are we filtering by term?
            if ( $search_term ) {
                $tax_query[ 'terms' ] = $search_term;
            }

            // Add the tax query to the args
            $args[ 'tax_query' ] = [ $tax_query ];
        }
        
        // Run the query
        $posts = new WP_Query( $args );

        // Make sure we found posts
        if ( $posts->have_posts() ) {

            // Add the count
            $results .= '<strong>Total: '.$posts->found_posts.'</strong><br><br>';

            // Start the outer container
            $results .= '<div class="ptf-outer-container">';

            // Iter the posts
            while ( $posts->have_posts() ) {

                // Initiate the post
                $posts->the_post();

                // Set the id
                $post_id = get_the_ID();

                // Get the title
                $title = get_the_title();

                // Check if there is a featured image
                $featured_img_url = get_the_post_thumbnail_url( $post_id, 'full' );
                if ( $featured_img_url ) {

                    // Get the image id
                    $image_id = get_post_thumbnail_id();

                    // Get alt text
                    if ( get_post_meta( $image_id, '_wp_attachment_image_alt', true ) && get_post_meta( $image_id, '_wp_attachment_image_alt', true ) != '' ) {
                        $image_alt = get_post_meta( $image_id, '_wp_attachment_image_alt', true );
                    } else {
                        $image_alt = $title;
                    }
                    
                    // Get the image title
                    if ( get_the_title( $image_id ) && get_the_title( $image_id ) != '' ) {
                        $image_title = get_the_title( $image_id );
                    } else {
                        $image_title = $title;
                    }
                    
                    // Add the featured image
                    $add_featured_image = '<div class="featured-img">
                        <a href="'.get_the_permalink().'" title="'.$image_title.'" style="outline: none;"><img src="'.$featured_img_url.'" alt="'.$image_alt.'"></a>
                    </div>';
                } else {
                    $add_featured_image = '';
                }

                // Get the excerpt
                if ( get_the_excerpt() && get_the_excerpt() != '' && get_the_excerpt() != ' ...' ) {
                    $excerpt = '<p>'.get_the_excerpt().'</p><br>';
                } else {
                    $excerpt = '';
                }                

                // Start the post container, add the title, excerpt, and thumbnail
                $container = '<div class="post-container">
                    '.$add_featured_image.'
                    <h4><a href="'.get_the_permalink().'">'.$title.'</a></h4>
                    '.$excerpt;

                    // Store the terms here
                    $add_terms = [];

                    // Iter the taxonomies
                    foreach ( $taxonomies as $taxonomy ) {

                        // Get the terms
                        $terms = get_the_terms( $post_id, $taxonomy );

                        // Iter the terms
                        foreach ( $terms as $term ) {

                            // Add the term to the array with current url link
                            $add_terms[] = '<a href="'.$current_url.'?tax='.$taxonomy.'&term='.$term->term_id.'">'.$term->name.'</a>';
                        }
                    }

                    // Add the terms to the container
                    $container .= implode( ', ', $add_terms );

                // End the container
                $container .= '</div>';

                // Add the container
                $results .= $container;
            }

            // End the outer container
            $results .= '</div>';

            // Add pagination links
            $results .= '<br></br><div class="page-nav-container">
                '.paginate_links( [
                    'base' => preg_replace( '/\?.*/', '/', get_pagenum_link(1) ) . '%_%',
                    'current' => max( 1, get_query_var( 'paged' ) ),
                    'format' => 'page/%#%',
                    'total' => $posts->max_num_pages,
                    'prev_text' => __('<'),
                    'next_text' => __('>'),
                    'add_args' => array(
                        'term' => get_query_var( 'term' )
                    )                    
                ] ) . '</div>';

        // Else say it isn't so
        } else {
            $results .= 'No posts found.';
        }

        // Return the results
        return $results;

    } // End shortcode()
}