Unable to differentiate between two categories under custom post type on single.php

Question

I have created A custom post type as mentioned in my older question

When I try to use get_the_category() function to retrieve the category of the post(if it is symphony or noir). It returns "Array". How can I keep the posts under the two categories separate which do not interfere in the pagination of one category.

     /*Custom post type 14K Gold and Silver*/
   function my_custom_post_14kgs() {
       $labels = array(
    'name'               => _x( '14k Gold & Silver', 'post type general name' ),
    'singular_name'      => _x( '14k Gold & Silver', 'post type singular name' ),
    'add_new'            => _x( 'Add New', 'book' ),
    'add_new_item'       => __( 'Add New Item' ),
    'edit_item'          => __( 'Modify Item' ),
    'new_item'           => __( 'New Item' ),
    'all_items'          => __( 'All Items' ),
    'view_item'          => __( 'View Item' ),
    'search_items'       => __( 'Search Items' ),
    'not_found'          => __( 'No Products found' ),
    'not_found_in_trash' => __( 'No products found in trash' ),
    'parent_item_colon'  => '',
    'menu_name'          => '14k Gold & Silver'
);
$args = array(
    'labels'        => $labels,
    'description'   => '',
    'public'        => true,
    'menu_position' => 5,
    'supports'      => array( 'title', 'editor', 'thumbnail', 'excerpt', 'comments' ),
    'has_archive'   => true,
    'hierarchical'  => true,
    'rewrite'       => array('slug' => '14k-gold-silver/%14kgscollection%','with_front' => false),
    'query_var'     => true,
    //'rewrite'     => true,
    //'publicly_queryable' => false,
);
register_post_type( '14kgs', $args );
   }
   add_action( 'init', 'my_custom_post_14kgs' );

   function my_taxonomies_product_14kgs() {
$labels = array(
    'name'              => _x( '14kgscollection', 'taxonomy general name' ),
    'singular_name'     => _x( '14kgscollection', 'taxonomy singular name' ),
    'search_items'      => __( 'Search Product Categories' ),
    'all_items'         => __( 'All Product Categories' ),
    'parent_item'       => __( 'Parent Product Category' ),
    'parent_item_colon' => __( 'Parent Product Category:' ),
           'edit_item'         => __( 'Edit Product Category' ),
           'update_item'       => __( 'Update Product Category' ),
           'add_new_item'      => __( 'Add New Product Category' ),
           'new_item_name'     => __( 'New Product Category' ),
           'menu_name'         => __( '14kgscollection' ),
       );
       $args = array(
                  'labels' => $labels,
                  'hierarchical'    => true,
                  'public'      => true,
                  'query_var'       => '14kgscollection',

                  'rewrite'     =>  array('slug' => '14k-gold-silver' ),
                  '_builtin'        => false,
       );
       register_taxonomy( '14kgscollection', '14kgs', $args );
   }
   add_action( 'init', 'my_taxonomies_product_14kgs', 0 );


   /*Filter permalink structure*/
   add_filter('post_link', 'collection14kgs_permalink', 1, 3);
   add_filter('post_type_link', 'collection14kgs_permalink', 1, 3);

   function collection14kgs_permalink($permalink, $post_id, $leavename) {
        if (strpos($permalink, '%14kgscollection%') === FALSE) return $permalink;
           // Get post
           $post = get_post($post_id);
            if (!$post) return $permalink;

            // Get taxonomy terms
            $terms = wp_get_object_terms($post->ID, '14kgscollection');
            if (!is_wp_error($terms) && !empty($terms) && is_object($terms[0]))
                $taxonomy_slug = $terms[0]->slug;
            else $taxonomy_slug = 'no-collection';

        return str_replace('%14kgscollection%', $taxonomy_slug, $permalink);
    }

Answer 1

Check the 3rd and 4th parameters for previous and next_post_link:

in_same_term (boolean) (optional) Indicates whether next post must be within the same taxonomy term as the current post. If set to 'true', only posts from the current taxonomy term will be displayed. If the post is in both the parent and subcategory, or more than one term, the next post link will lead to the next post in any of those terms. true false Default: false

excluded_terms (string/array) (optional) Array or a comma-separated list of numeric terms IDs from which the next post should not be listed. For example array(1, 5) or '1,5'. This argument used to accept a list of IDs separated by 'and', this was deprecated in WordPress 3.3

Default: None

Also, you may find creating custom taxonomy types better for use with CPT's than categories.

add_action( 'init', 'video_type_taxonomy' );
function video_type_taxonomy() {

    register_taxonomy( 'video-type', 'video',
        array(
            'labels' => array(
                'name'          => _x( 'Types', 'taxonomy general name', 'executive' ),
                'add_new_item'  => __( 'Add New Video Type', '$text_domain' ),
                'new_item_name' => __( 'New Video Type', '$text_domain' ),
            ),
            'exclude_from_search' => true,
            'has_archive'         => true,
            'hierarchical'        => true,
            'rewrite'             => array( 'slug' => 'video-type', 'with_front' => false ),
            'show_ui'             => true,
            'show_tagcloud'       => false,
        )
    );

}

Answer 2

get_next_post ( ) and get_previous_post ( ) helped in getting what I was looking for.

Thanx all for your time