create next previous post for custom post type

functions.php

// create next previous page for custom post type
function get_prevnext_custompost($post_ID, $postType, $taxonomy, $term) {
    if($taxonomy){    
        $args = array(
            'post_type' => $postType,
            'posts_per_page' => -1,
            'post_status' => 'publish',
            'tax_query' => array(
                array(
                    'taxonomy' => $taxonomy,
                    'field' => 'term_id',
                    'terms' => $term
                )
            )
        );
    }else{
        $args = array(
            'post_type' => $postType,
            'posts_per_page' => -1,
            'post_status' => 'publish'
        );
    }

    $all_posts = get_posts($args);

    $next_post_id = null;
    $prev_post_id = null;

    if(!empty($all_posts)){
        //Get total post in the array
        $post_id_array = [];
        foreach ($all_posts as $postKey => $postValue) {
            $post_id_array[] = $postValue->ID;
        }

        //echo '<pre>'; print_r($post_id_array); echo '</pre>';
        // check current post in the array and return its key index
        $currentPostkey = array_search ($post_ID, $post_id_array);
        //echo '$currentPostkey: '.$currentPostkey;

        // Get total element in the array
        $totalArrayElement = count($post_id_array);
        //echo '$totalArrayElement: '.$totalArrayElement;

        //echo '$post_ID: '.$post_ID;        

        //Calculate next and previous id
        if($totalArrayElement > 1){
            if($currentPostkey && $currentPostkey == 0){
                $next_post_id = $post_id_array[$currentPostkey + 1];       
                $prev_post_id = $post_id_array[$totalArrayElement - 1];     
            }elseif($currentPostkey && $currentPostkey + 1 == $totalArrayElement){            
                $prev_post_id = $post_id_array[$currentPostkey - 1];
                $next_post_id = $post_id_array[0];
            }else{
                $next_post_id = $post_id_array[$currentPostkey + 1];
                $prev_post_id = $post_id_array[$currentPostkey - 1];
            }
        }
    }

    return array($prev_post_id, $next_post_id);
}

//=========================================================================================
// Apply on template

list($previousPostId, $nextpostId) = get_prevnext_custompost($pdIds, 'ebook', '', null);

$next_post = get_post($nextpostId);
if ( !empty( $next_post ) ) {
    $next_post_url = get_permalink( $next_post->ID );

}
$prev_post = get_post($previousPostId);
if ( !empty( $prev_post ) ) {
    $prev_post_url = get_permalink( $prev_post->ID );

}