Scott Reilly

This plugin provides two template tags for use in single.php to create a post navigation loop, whereby previous to the first post is the last post, and after the last post is first post. Basically, when you’re on the last post and you click to go to the next post, the link takes you to the first post. Likewise, if you’re on the first post and click to go to the previous post, the link takes you to the last post.
The function <code>c2c_next_or_loop_post_link()</code> is identical to WordPress’s <code>next_post_link()</code> in every way except when called on the last post in the navigation sequence, in which case it links back to the first post in the navigation sequence.
The function <code>c2c_previous_or_loop_post_link()</code> is identical to WordPress’s <code>previous_post_link()</code> in every way except when called on the first post in the navigation sequence, in which case it links back to the last post in the navigation sequence.
Useful for providing a looping link of posts, such as for a portfolio, or to continually present pertinent posts for visitors to continue reading.
If you are interested in getting the post itself and not just a link to the post, you can use the <code>c2c_get_next_or_loop_post()</code> and <code>c2c_get_previous_or_loop_post()</code> functions. If you just want the URL to the post, you can use <code>c2c_get_next_or_loop_post_url()</code> and <code>c2c_get_previous_or_loop_post_url()</code>.
Links: <a href="https://coffee2code.com/wp-plugins/loop-post-navigation-links/" rel="nofollow ugc">Plugin Homepage</a> | <a href="https://wordpress.org/plugins/loop-post-navigation-links/" rel="ugc">Plugin Directory Page</a> | <a href="https://github.com/coffee2code/loop-post-navigation-links/" rel="nofollow ugc">GitHub</a> | <a href="https://coffee2code.com" rel="nofollow ugc">Author Homepage</a>
<h3>Template Tags</h3>
The plugin provides four template tags for use in your single-post theme templates.
<h4>Functions</h4>
<ul>
<li>
<code>function c2c_next_or_loop_post_link( $format='%link &raquo;', $link='%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' )</code> 
Like WordPress’s <code>next_post_link()</code>, this function displays a link to the next chronological post (among all published posts, those in the same category, or those not in certain categories). Unlink <code>next_post_link()</code>, when on the last post in the sequence this function will link back to the first post in the sequence, creating a circular loop.
</li>
<li>
<code>function c2c_get_next_or_loop_post_link( $format='%link &raquo;', $link='%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' )</code> 
Like `c2c_next_or_loop_post_link(), but returns the value without echoing it.
</li>
<li>
<code>function c2c_previous_or_loop_post_link( $format='&laquo; %link', $link='%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' )</code> 
Like WordPress’s <code>previous_post_link()</code>, this function displays a link to the previous chronological post (among all published posts, those in the same category, or those not in certain categories). Unlink <code>previous_post_link()</code>, when on the first post in the sequence this function will link to the last post in the sequence, creating a circular loop.
</li>
<li>
<code>function c2c_get_previous_or_loop_post_link( $format='&laquo; %link', $link='%title', $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' )</code> 
Like `c2c_get_previous_or_loop_post_link(), but returns the value without echoing it.
</li>
<li>
<code>function c2c_get_next_or_loop_post( $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' )</code> 
Like WordPress’s <code>get_adjacent_post()</code> when used to find the next post, except when on the last post in the sequence this function will return the first post in the sequence, creating a circular loop.
</li>
<li>
<code>function c2c_get_previous_or_loop_post( $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' )</code> 
Like WordPress’s <code>get_adjacent_post()</code> when used to find the previous post, except when on the first post in the sequence this function will return the last post in the sequence, creating a circular loop.
</li>
<li>
<code>function c2c_get_next_or_loop_post_url( $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' )</code> 
Returns the URL for the next post or the post at the beginning of the series.
</li>
<li>
<code>function c2c_get_previous_or_loop_post_url( $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' )</code> 
Returns the URL for the previous post or the post at the end of the series.
</li>
</ul>
<h4>Arguments</h4>
<ul>
<li>
<code>$format</code> 
(optional) A percent-substitution string indicating the format of the entire output string. Use <code>%link</code> to represent the next/previous post being linked, or <code>%title</code> to represent the title of the next/previous post.
</li>
<li>
<code>$link</code> 
(optional) A percent-substitution string indicating the format of the link itself that gets created for the next/previous post. Use <code>%link</code> to represent the next/previous post being linked, or <code>%title</code> to represent the title of the next/previous post.
</li>
<li>
<code>$in_same_term</code> 
(optional) A boolean value (either true or false) indicating if the next/previous post should be in the current post’s same taxonomy term.
</li>
<li>
<code>$excluded_terms</code> 
(optional) An array or comma-separated string of category or term IDs to which posts cannot belong.
</li>
<li>
<code>$taxonomy</code> 
(optional) Taxonomy, if $in_same_term is true. Default ‘category’.
</li>
</ul>
<h3>Examples</h3>
<pre><code><div class="loop-navigation">
 <div class="alignleft"><?php c2c_previous_or_loop_post_link(); ?></div>
 <div class="alignright"><?php c2c_next_or_loop_post_link(); ?></div>
</div><h3>Hooks</h3>
</code></pre>
The plugin is further customizable via eleven hooks. Typically, code making use of hooks should ideally be put into a mu-plugin, a site-specific plugin (which is beyond the scope of this readme to explain), or in theme template files. Many of these filters are likely only of interest to advanced users able to code.
c2c_previous_or_loop_post_link_output, c2c_next_or_loop_post_link_output (filters)
The ‘c2c_previous_or_loop_post_link_output’ and ‘c2c_next_or_loop_post_link_output’ filters allow you to customize the link markup generated for previous and next looping links, respectively.
Arguments:
<ul>
<li>$format (string): Link anchor format.</li>
<li>$link (string): Link permalink format.</li>
<li>$in_same_term (bool): Optional. Whether link should be in a same taxonomy term. Default is false.</li>
<li>$excluded_terms (array|string): Optional. Array or comma-separated list of excluded term IDs. Default is ”.</li>
<li>$previous (bool): Optional. Whether to display link to previous or next post. Default is true.</li>
<li>$taxonomy (string): Optional. Taxonomy, if $in_same_term is true. Default ‘category’.</li>
<li>$adjacent (string): Whether the post is previous or next.</li>
</ul>
Example:
<pre><code> <?php
 // Prepend "Prev:" to previous link markup.
 function my_custom_previous_or_loop_link_output( $output, $format, $link, $post, $in_same_term, $excluded_terms, $taxonomy ) {
 return 'Prev: ' . $output;
 }
 add_filter( 'c2c_previous_or_loop_post_link_output', 'my_custom_previous_or_loop_link_output', 10, 4 );
 ?>
</code></pre>
c2c_previous_or_loop_post_link_get, c2c_next_or_loop_post_link_get (filters)
The ‘c2c_previous_or_loop_post_link_get’ and ‘c2c_next_or_loop_post_link_get’ filters allow you to customize the link markups generated for previous and next looping links, respectively, but in the non-echoing functions.
Arguments:
<ul>
<li>$output (string): The adjacent post link.</li>
<li>$format (string): Link anchor format.</li>
<li>$link (string): Link permalink format.</li>
<li>$post (WP_Post): The adjacent post.</li>
<li>$in_same_term (bool): Optional. Whether link should be in a same taxonomy term. Default is false.</li>
<li>$excluded_terms (array|string): Optional. Array or comma-separated list of excluded term IDs. Default is ”.</li>
<li>$previous (bool): Optional. Whether to display link to previous or next post. Default is true.</li>
<li>$taxonomy (string): Optional. Taxonomy, if $in_same_term is true. Default ‘category’.</li>
<li>$adjacent (string): Whether the post is previous or next.</li>
</ul>
c2c_previous_or_loop_post_link, c2c_next_or_loop_post_link, c2c_get_previous_or_loop_post_link, c2c_get_next_or_loop_post_link, c2c_get_adjacent_or_loop_post, c2c_get_previous_or_loop_post, c2c_get_previous_or_loop_post (actions)
The ‘c2c_previous_or_loop_post_link’ and ‘c2c_next_or_loop_post_link’ actions allow you to use an alternative approach to safely invoke <code>c2c_previous_or_loop_post_link()</code> and <code>c2c_next_or_loop_post_link()</code>, respectively, in such a way that if the plugin were deactivated or deleted, then your calls to the functions won’t cause errors in your site. The ‘c2c_get_previous_or_loop_post_link’ and ‘c2c_get_next_or_loop_post_link’ filters do the same for the non-echoing <code>c2c_previous_or_loop_post_link()</code> and <code>c2c_next_or_loop_post_link()</code>.
Arguments:
<ul>
<li>Same as for for <code>c2c_previous_or_loop_post_link()</code> and <code>c2c_next_or_loop_post_link()</code></li>
</ul>
Example:
Instead of:
<pre><code><?php c2c_previous_or_loop_post_link( '&laquo; %link' ); ?>
</code></pre>
Do:
<pre><code><?php do_action( 'c2c_previous_or_loop_post_link', '&laquo; %link' ); ?>
</code></pre>

Loop Post Navigation Links

Template tags (for use in single.php) to create post navigation loop (previous to first post is last post; next/after last post is first post).

CrestaProject

<a href="https://crestaproject.com/downloads/cresta-posts-box/" rel="nofollow ugc">Plugin Homepage & Demo</a>
With Cresta Posts Box you can show, in a single page (posts, pages or custom post types), a small box that allows the reader to go to the next or previous post. The box appears only when the reader finishes reading the current post.
Some features
<ul>
<li>Choose to show next or previous post</li>
<li>Choose the box position (left or right)</li>
<li>Choose the font size</li>
<li>Choose the box width</li>
<li>and more…</li>
</ul>
PRO version features
<ul>
<li>Show Random Post</li>
<li>Show Related Post</li>
<li>Set box background color</li>
<li>Set box text and link color</li>
<li>Set border box and border radius box</li>
<li>5 Animations</li>
<li>and much more…</li>
</ul>

Cresta Posts Box

In free version, you have to chose to show only previous or next post. Too limited to be really useful.

Too poor in free version

Show the next or previous post in a box that appears when the user scrolls to the bottom of a current post.

Loop Post Navigation Links vs Cresta Posts Box