[WordPress Related Post]

related-posts-2.php

<?php
	/*
	 * Plugin Name: Related Post
	*/
	
	function pippin_related_posts( $taxonomy = '' ) {
		global $post;
		
		if ( $taxonomy == '' ) {
			$taxonomy = 'post_tag';
		}
		
		$tags = wp_get_post_terms( $post->ID, $taxonomy );
		
		if ( $tags ) {
			$first_tag  = $tags[0]->term_id;
			$second_tag = $tags[1]->term_id;
			$third_tag  = $tags[2]->term_id;
			$args       = array(
				'post_type'      => get_post_type( $post->ID ),
				'posts_per_page' => 4,
				'tax_query'      => array(
					'relation' => 'OR',
					array(
						'taxonomy' => $taxonomy,
						'terms'    => $second_tag,
						'field'    => 'id',
						'operator' => 'IN',
					),
					array(
						'taxonomy' => $taxonomy,
						'terms'    => $first_tag,
						'field'    => 'id',
						'operator' => 'IN',
					),
					array(
						'taxonomy' => $taxonomy,
						'terms'    => $third_tag,
						'field'    => 'id',
						'operator' => 'IN',
					)
				)
			);
			$related    = get_posts( $args );
			$i          = 0;
			if ( $related ) {
				global $post;
				$temp_post = $post;
				foreach ( $related as $post ) : setup_postdata( $post );
					$content .= '<ul class="related-posts-box">';
					$content .= '<li><a href="' . get_permalink() . '" title="' . get_the_title() . '">' . get_the_title() . '</a></li>';
					$content .= '</ul>';
				
				endforeach;
				$post = $temp_post;
			}
		}
		
		return $content;
	}
	
	function do_jt_related_posts() {
		if ( is_singular( 'post' ) ) :
			echo get_the_content();
			echo pippin_related_posts();
		else :
			echo get_the_content();
		endif;
	}
	
	add_action( 'the_content', 'do_jt_related_posts' );

related-posts.php

<?php
if ( is_singular( 'post' ) ) {
	$aa_show_all_posts = true;
	$aa_show_from_cat  = true;
	$tag_ids           = array();
	$category_ids      = array();
	
	$tags = wp_get_post_tags( get_the_ID() );
	
	if ( ! empty( $tags ) ) {
		foreach ( $tags as $tag ) {
			$tag_ids[] = $tag->term_id;
			
			if ( $aa_show_from_cat == false ) {
				continue;
			}
			
			$aa_show_from_cat = $tag->count > 1 ? false : true;
		}
	}
	
	if ( $aa_show_from_cat ) {
		$categories = get_the_category( get_the_ID() );
		
		if ( ! empty( $categories ) ) {
			foreach ( $categories as $category ) {
				$category_ids[] = $category->term_id;
				
				if ( $aa_show_all_posts == false ) {
					continue;
				}
				
				$aa_show_all_posts = $category->count > 1 ? false : true;
			}
		}
	}
	
	$args = array(
		'post_type'      => 'post',
		'posts_per_page' => 4,
		'post__not_in'   => array( get_the_ID() )
	);
	
	$args['tag__in'] = $tag_ids;
	
	if ( ! $aa_show_all_posts ) {
		$args['category__in'] = $category_ids;
	}
	
	$related_posts = new WP_Query( $args );
	?>
	<div class="app-box related-posts">
		<div class="row">
			<div class="col-12">
				<h3 class="fa-title"><?php _e( 'Related Posts', AA_THEME_SLUG ); ?></h3>
			</div>
		</div>
		<div class="row app-box-content">
			<?php
			if ( $related_posts->have_posts() ) :
				$related_posts_num = 1;
				?>
				<?php while ( $related_posts->have_posts() ) : ?>
				<?php $related_posts->the_post(); ?>
				<div class="col-12 text-center text-md-left col-md-<?php echo $related_posts->post_count > 3 ? '3' : '4';
				echo $related_posts_num != 1 ? ' mt-5 mt-md-0' : ''; ?>">
					<?php if ( has_post_thumbnail() ) : ?>
						<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
							<?php the_post_thumbnail( 'medium', array( 'class' => 'post-img' ) ); ?>
						</a>
					<?php endif; ?>
					<h3 class="post-title">
						<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
							<?php echo esc_html( wp_trim_words( get_the_title(), 5, '...' ) ); ?>
						</a>
					</h3>
					<p class="post-excerpt">
						<?php echo esc_html( wp_trim_words( get_the_excerpt(), 20, '...' ) ); ?>
					</p>
				</div>
				<?php $related_posts_num ++; ?>
			<?php endwhile; ?>
			<?php else : ?>
				<div class="col-12">
					No Related Post Found!
				</div>
			<?php endif; ?>
		</div>
	</div>
	<?php wp_reset_postdata();
}