Using custom taxonomy to tag posts for inclusion in slider

Question

I'm confused how to properly tackle this and the amount of information on the subject isn't very direct. I am trying to develop a custom slider for my homepage and needed to create a custom taxonomy 'slider' to tag which posts could be included in the slideshow.

Here's the code I used:

add_action( 'init', 'create_slider_taxonomies', 0 );

function create_slider_taxonomies() {
    $labels = array(
        'name'              => _x( 'Sliders', 'taxonomy general name', 'textdomain' ),
        'singular_name'     => _x( 'Slider', 'taxonomy singular name', 'textdomain' ),
        'search_items'      => __( 'Search Sliders', 'textdomain' ),
        'all_items'         => __( 'All Sliders', 'textdomain' ),
        'parent_item'       => __( 'Parent Slider', 'textdomain' ),
        'parent_item_colon' => __( 'Parent Slider:', 'textdomain' ),
        'edit_item'         => __( 'Edit Slider', 'textdomain' ),
        'update_item'       => __( 'Update Slider', 'textdomain' ),
        'add_new_item'      => __( 'Add New Slider', 'textdomain' ),
        'new_item_name'     => __( 'New Slider Name', 'textdomain' ),
        'menu_name'         => __( 'Slider', 'textdomain' ),
    );


    $args = array(
        'hierarchical'      => true,
        'labels'            => $labels,
        'show_ui'           => true,
        'show_admin_column' => true,
        'query_var'         => true,
        'rewrite'           => array( 'slug' => 'slider' ),
        'show_in_rest'      => true, // need to show this in order for option to display under the 'Document' panel in a post
    );

    register_taxonomy( 'slider', array( 'post', 'slider' ), $args );
}

And it showed up in the post just fine:

Now, I'm unsure how to query a list of the posts so that I can assemble the content onto a page.

I thought that I could do some variation of my $wp_query that I use for the archive page, but that didn't seem to work:

<?php 
$temp = $wp_query; $wp_query= null;
$wp_query = new WP_Query(); 
$wp_query->query(array(
  'posts_per_page' => -1,
  'taxonomy'       => slider,
  'field'          => slug,
  'terms'          => homepage
));
while ($wp_query->have_posts()) : $wp_query->the_post(); ?>

Maybe this isn't the best way to do this. But I don't want to rely on yet another third party plugin especially when the majority of slider plugins don't feature content the way that I want them to.

Any suggestions will be appreciated. Thank you!

Answer 1

Remember to wrap your strings in quotes. I think that's the main issue. This works for me:

<?php
// https://developer.wordpress.org/reference/classes/wp_query/#taxonomy-parameters
// Set up a new WP_Query object for posts that have the 'homepage' term
// set for the 'slider' taxonomy:
$slide_query = new WP_Query( array(
    'posts_per_page' => 100, // Set a reasonable limit just in case.
    'post_type'      => 'post',
    'tax_query'  => array(
        array(
            'taxonomy' => 'slider', // Strings should have quotes!
            'field'    => 'slug',
            'terms'    => 'homepage',
        ),
    ),
));
?>

Then output the HTML:

<?php if ( $slide_query->have_posts() ) : ?>
    <div class="slider">
        <?php while ( $slide_query->have_posts() ) : $slide_query->the_post(); ?>
            <div class="slide">
                <h2 class="slide-title">><?php the_title(); ?></h2>
                <div class="slide-content">
                    <?php the_content(); ?>
                </div>
            </div>
        <?php endwhile; ?>
    </div>
<?php wp_reset_postdata(); ?>
<?php endif; ?>

You don't need to do the $temp = $wp_query; $wp_query= null; thing. Just create a new variable like I did in the example, and call wp_reset_postdata() as I did in the example.