Combine 2 arrays in a query parameter

Question

I'm trying to exclude upsells using post__not_in but I already have a value and do not know how to combine the two.

I tried this:

'post__not_in' => get_upsell_ids(), [get_the_ID()]

But it is not working.

My code:

function eligo_custom_related_products_by_label() {
    
    if (is_product() && has_term('records', 'product_cat')) {

        global $post;

        if ( ! $post ) {
            return;
        }

        $related_by_same_label = wp_get_post_terms($post->ID, 'pa_label', ['fields' => 'slugs']);

        $args = [
            'post_type' => 'product',
            'post_status' => 'publish',
            'orderby' => 'rand',
            'posts_per_page' => 4,
            'post__not_in' => [get_the_ID()],
            'tax_query' => [
                'relation' => 'AND',
                [
                    'taxonomy' => 'product_visibility',
                    'field'    => 'name',
                    'terms'    => array('outofstock'),
                    'operator' => 'NOT IN'
                ],
                [
                    'taxonomy' => 'pa_label',
                    'field' => 'slug',
                    'terms' => $related_by_same_label,
                    'operator' => 'IN',
                ],
            ],
        ];

        $loop = new WP_Query($args);

        if ($loop->have_posts()) { ?>

            <section class="related products">
                <div class="related__inner">
                    <?php
                    $attribute_names = ['pa_label'];
                    foreach ($attribute_names as $attribute_name) {
                        $taxonomy = get_taxonomy($attribute_name);
                        if ($taxonomy && !is_wp_error($taxonomy)) {
                            $terms = wp_get_post_terms($post->ID, $attribute_name);
                            $terms_array = [];
                            if (!empty($terms)) {
                                foreach ($terms as $term) {
                                    $archive_link = get_term_link($term->slug, $attribute_name);
                                    $full_line = '<a href="' . $archive_link . '">' . $term->name . '</a>';
                                    array_push($terms_array, $full_line);
                                }
                                echo '<h3 class="section__title">' . esc_html__('More from', 'eligo') . ': ' . implode(', ', $terms_array) . '</h3>';
                            }
                        }
                    }

                    woocommerce_product_loop_start(); 

                    while ($loop->have_posts()):
                        $loop->the_post();
                        wc_get_template_part('content', 'product');
                    endwhile;
                    
                    ?>
                </div>
            </section>
            <?php

        } 

        wp_reset_postdata();
    }
}
add_action('woocommerce_after_single_product_summary', 'eligo_custom_related_products_by_label', 20);

Thanks in advance.

Answer 1

This does not work because this is not how you merge two arrays:

'post__not_in' => get_upsell_ids(), [get_the_ID()]

Instead you need to take those 2 arrays and combine them using array_merge, a standard PHP function:

https://www.php.net/manual/en/function.array-merge.php

Note that __not_in type parameters have a very high performance cost and do not scale, this query will be very slow and require caching.