link directly to custom post if there is only one in the taxonomy

I have this code in my custom-taxonomy.php file.

        if ( have_posts() ) :

            //do_action( 'generate_archive_title' );
            $term = get_queried_object();
            $term_id = $term->term_id;
            $taxonomy_name = $term->taxonomy;
            $termchildren = get_terms( array(
                'taxonomy' => $taxonomy_name,
                'parent' => $term_id
            ));
            $secondimg = get_field('secondary_img', $term);
            ?>

            <header class="page-header">
                <h1 class="page-title"><?php single_cat_title(); ?></h1>
                <?php
                if ( ! empty( term_description() ) ) :
                    printf( '<div class="taxonomy-description">%s</div>', term_description() );
                endif;
                if ( $secondimg ) echo '<img src="'.$secondimg['url'].'" alt="our image">';
                ?>
            </header>

            <?php

            if ( $termchildren  ) {
                // we have kids...just show the terms.
                $howmany = count($termchildren);
                $i=1;
                foreach ( $termchildren as $child ) {
                    if ($i % 2 == 0) {
                        echo '<div class="tax-entry flex '.$howmany.'">';
                    } else {
                        echo '<div class="tax-entry flex '.$howmany.'" style="flex-direction: row-reverse;">';
                    }
                    ?>
                        <figure class="wp-block-media-text__media">
                            <?php if ( get_field('product_category_img', $child) ) echo wp_get_attachment_image( get_field('product_category_img', $child), 'full' ) ;?>
                        </figure>
                        <div style="flex:60% 0 0;" class="wp-block-media-text__content">
                            <h2><?php echo $child->name ;?></h2>
                            <p>
                                <?php
                                if (get_field('short_description', $child )){ 
                                    echo get_field('short_description', $child );
                                }else{
                                    echo $child->description;
                                }?>
                            </p>
                            <a class="button" href="<?php echo get_term_link( $child, $taxonomy_name ) ;?>">See this Series</a>

                        </div>
                    </div> <!-- END FLEX -->
                    <?php
                    $i++;
                }
            } else { 
                // no kids...show the products
                echo '<div class="productCategories grid">';
                while ( have_posts() ) : the_post();
                    ?>

                    <div class="product_cat">
                        <a href="<?php the_permalink();?>">
                            <?php the_post_thumbnail('small');?>
                            <h2><?php the_title();?></h2>
                <?php
                $subtitle = the_field('subtitle');
                if ( $subtitle ) { 
                  echo '<h3 class="entry-subtitle">'.$subtitle.'</h3>';
                }
                 ?>
                        </a>
                        <?php //if (get_field('specs')['part_number']) echo '<span>'.get_field('specs')['part_number'].'</span>';?>
                    </div>

                <?php
                endwhile;
                echo '</div>';
            }

            /**
             * generate_after_loop hook.
             *
             * @since 2.3
             */
            do_action( 'generate_after_loop' );

            generate_content_nav( 'nav-below' );

        else :

            get_template_part( 'no-results', 'archive' );

        endif;

I’m trying to figure out if there is a method to change the link on this line:

<a class="button" href="<?php echo get_term_link( $child, $taxonomy_name ) ;?>">See this Series</a>

so that if the term only has one product it will link to that product itself.

Is this possible?

Answers:

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Method 1

How about doing it this way:

<?php
// Get (at most) 2 "product" posts in the child term.
$posts = get_posts( array(
    'post_type'      => 'product', // just change the post type if it is not "product"
    'posts_per_page' => 2,
    $taxonomy_name   => $child->slug,
) );

// If there's exactly 1 post, use the post permalink.
if ( 1 === count( $posts ) ) : ?>
    <a class="button" href="<?php the_permalink( $posts[0] ); ?>">See this Product</a>
<?php // Else, use the term link.
else : ?>
    <a class="button" href="<?php echo esc_url( get_term_link( $child, $taxonomy_name ) ); ?>">See this Series</a>
<?php endif; ?>

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