I'm busy rewritting a custom function I have recently written to get adjacent posts according to a tag, category, custom taxonomy term, author or search value saved in the URL

I'm busy rewritting a custom function I have recently written to get adjacent posts according to a tag, category, custom taxonomy term, author or search value saved in the URL

Here is what I have (just is rough draught for testing). This gets an adjacent post

$where = '';

$join = '';
$op = '>';
$order = 'ASC';
$current_post_date = $post->post_date;
$post_type = $post->post_type;
$category = 1;
$where = $wpdb->prepare( "WHERE p.post_date $op %s AND p.post_type = %s AND p.post_status = 'publish' $where", $current_post_date, $post_type );
$sort = "ORDER BY p.post_date $order LIMIT 1";
$query = $wpdb->get_results("SELECT p.ID FROM $wpdb->posts AS p $join $where $sort");

Now, to get adjacent posts from posts belonging to the same, for tag, category or term according to the value in the URL, I can simply add a join like this

$join = $wpdb->prepare( " INNER JOIN $wpdb->term_relationships AS tr ON p.ID = tr.object_id  AND tr.term_taxonomy_id IN (%s)", $term );  

or for authors

$where .= $wpdb->prepare( "AND p.post_author IN (%s)", $author );

This works fine, but I cannot get anything to work for a search query. If my search query is rocks, how do I get the next and previous post in my search query rocks

Here is what I have. This successfully retrieves the ID of the adjacent post and returns it according to the query_vars set in the URL. If no custom query_vars are set, the function gets the adjacent post in normal chronological order as normal

<?php    
function get_adjacent_include_referred_post( $previous = true ) {
    global $wpdb;

    if ( ( ! $post = get_post() ) )
        return null;

    $current_post_date = $post->post_date;

    $join = '';
    $where = '';

    //Alter the SQL query if 'aq' is set in single page URL
    if( is_author_referrer() ) {
    
        $author = $_GET['aq'];
        $where .= $wpdb->prepare( "AND p.post_author IN (%s)", $author );
    
    }
    
    //Alter the SQL query if 'tq' is set in single page URL
    if( is_tax_referrer() ) {
    
        $term = $_GET['tq'];
        $join = $wpdb->prepare( " INNER JOIN $wpdb->term_relationships AS tr ON p.ID = tr.object_id  AND tr.term_taxonomy_id IN (%s)", $term );
    
    }
    
    //Alter the the SQL query if sq is set in single page URL
    if( is_search_referrer() ) {
    
        $term = $_GET['sq'];
        // **MISSING INFO** 
    }
    
    
    //Set next and previous post's operators to form the SQL query
    $adjacent   = $previous ? 'previous' : 'next';
    $op         = $previous ? '<' : '>';
    $order      = $previous ? 'DESC' : 'ASC';
    
    // Setting the default clauses to build the custom SQL query to get adjacent post
    $where = $wpdb->prepare( "WHERE p.post_date $op %s AND p.post_type = %s AND p.post_status = 'publish' $where", $current_post_date, $post->post_type );
    $sort  = "ORDER BY p.post_date $order LIMIT 1";
    $query = "SELECT p.ID FROM $wpdb->posts AS p $join $where $sort";
 
    //Create and set cache to improve performance of the function
    $query_key = 'get_the_adjacent_post_' . md5( $query );
    $result = wp_cache_get( $query_key, 'counts' );
    
    $result = $wpdb->get_var( $query );
    if ( null === $result )
        $result = '';

    wp_cache_set( $query_key, $result, 'counts' ); 

    return $result;

}

My problem, I cannot get anything to work for a search query (my SQL knowledge is just to poor to assemble something useful). If my search query is rocks and someone clicks on a single post, how do I adjust my SQL query to get the adjacent post from the current single post being viewed within the same search query?

FEW NOTES ON MY CODE

• The is_***_referrer() conditional checks are wrapper functions which checks if the appropriate S_GET['***'] is set. For the search query, is_search_referrer() checks if $_GET['sq'] is set, returns true if the query_vars exists, false on failure

• The value of $_GET['sq'] will is the value of get_search_query(). This is the value that should be used to get the adjacent post for the same search query

• There is no syntax errors in my code and it works. I know the code looks funny for some reason in the code block above, and it does seem from that that there are syntax errors, but there aren't.