Why is next_post_link() not working with WP_Query? - php

Question

Been researching a pagination issue I am having with WordPress. My page-foobar.php file is:
<?php
// the query
$foobar_args = array( 'post_type' => 'foobar', 'posts_per_page' => 4, 'ignore_sticky_posts' => true, );
$foo_query = new WP_Query( $foobar_args );
if ( $foo_query->have_posts() ) : ?>
<?php while ( $foo_query->have_posts() ) : $foo_query->the_post();?>
// code
<?php endwhile; ?>
<?php wp_reset_postdata(); ?>
<?php else : ?>
<p><?php _e( 'Sorry, no foobar posts at this time.', 'theme' ); ?></p>
<?php endif; ?>
I added:
<nav>
<?php previous_posts_link('« Newer',$foo_query->max_num_pages); ?>
<?php next_posts_link('Older »',$foo_query->max_num_pages); ?>
</nav>
after referencing this answer after the endif;:
The link shows in the url as site/foobar/page/2/ but displays the 404 page. After some further research I ran across an article that mentioned the page-foobar.php and posttype-foobar.php names can clash so to rename one of them. I renamed posttype-foobar2.php, changed my functions.php, tested and still get sent to the 404 page with the correct URL. Another article mentioned that you must use wp_query() so I changed my page-foobar.php to:
<?php
// the query
$foobar_args = array( 'post_type' => 'foobar', 'posts_per_page' => 4, 'ignore_sticky_posts' => true, );
$wp_query = new WP_Query( $foobar_args );
if ( $wp_query->have_posts() ) : ?>
<?php while ( $wp_query->have_posts() ) : $wp_query->the_post();?>
// code
<?php endwhile; ?>
<?php wp_reset_postdata(); ?>
<?php else : ?>
<p><?php _e( 'Sorry, no foobar posts at this time.', 'theme' ); ?></p>
<?php endif; ?>
pagination:
<nav>
<?php previous_posts_link('« Newer',$wp_query->max_num_pages); ?>
<?php next_posts_link('Older »',$wp_query->max_num_pages); ?>
</nav>
I did test this by adding this before <?php wp_reset_postdata(); ?> and after <?php endwhile; ?>:
<nav>
<?php previous_posts_link('« Newer',$wp_query->max_num_pages); ?>
<?php next_posts_link('Older »',$wp_query->max_num_pages); ?>
</nav>
tested and I still get sent to a 404 page. When I change next_posts_link() to <?php var_dump(next_posts_link('« Older Entries', $wp_query->max_num_pages)); ?> it returns NULL. If I change next_posts_link() to get_next_posts_link() I get string(99). What am I doing wrong with my pagination?
Further Referenced:
Wordpress pagination (next_posts_link) on custom wp_query not showing
next_posts_link 404 error
WP_Query and next_posts_link
How can I properly get my pagination to go to the next page?

Answer 1

// the query
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$foobar_args = array( 'post_type' => 'foobar', 'posts_per_page' => 4, 'paged' => $paged);
$wp_query = new WP_Query( $foobar_args );
if ( $wp_query->have_posts() ) : ?>
<?php while ( $wp_query->have_posts() ) : $wp_query->the_post();?>
<?php the_title(); echo "<br/>"; ?>
<?php endwhile; ?>
<nav>
<?php previous_posts_link('« Newer',$wp_query->max_num_pages); ?>
<?php next_posts_link('Older »',$wp_query->max_num_pages); ?>
</nav>
<?php wp_reset_postdata(); ?>
<?php else : ?>
<p><?php _e( 'Sorry, no foobar posts at this time.', 'theme' ); ?></p>
<?php endif; ?>

Answer 2

After doing some further research I ran across the solution to my problem and I hope it can help someone else. The answer submitted by Sindhu does have merit in respect to the addition of:
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
and the modification to the arguments:
$foobar_args = array( 'post_type' => 'foobar', 'posts_per_page' => 4, 'paged' => $paged);
Codex for get_query_var(). After making this additional change it still didn't work so I started testing my Permalinks. When I ran the code under Default the pagination worked. When I changed to Post name and saved twice it still didn't work. After browsing I decided to search for custom post type giving 404 error and I ran across "Fixing Custom Post Type 404 Errors In WordPress" which mentioned I could be creating a double slug. After review I was in fact doing so and WordPress was clashing with the double slug. I decided to changed my posttype-foobar.php to posttype-foobar_t.php and updated my functions.php file. Instead of modifying the database on my localhost to fix the slug issue I decided to install a clean installation with the modified changes and it works.
I would also like to point out some of my findings in regards to a large majority of posts mentioned you have to call the query as $wp_query = new WP_Query( $foobar_args );.