Limit search field to just search a custom post type with custom fields

Question

I'm sure this is possible, I just don't think I am going the right way about it. Basically, I have two custom post types (Investigators & Centres), both of which have search forms on their respective archive pages (below) to filter the archive based on a users input and custom fields (which are being indexed by the Custom fields search plugin).

http://dev.anklearthritis.co.uk/find-a-specialist/ (Investigators) http://dev.anklearthritis.co.uk/centres/ (Centres)

At the moment however, no matter what the user searches, the first 6 entries are always shown.

I'm using the following query (for investigators) in my search file

$args = array( 
    'post_type' => 'investigator', 
    'paged' => $paged,
    'orderby' => 'title',
    'order' => 'ASC',
    'posts_per_page' => 6, //Limits the amount of posts on each page
    'post_title' => 'LIKE %'.$_POST['s'].'%' 
);
$loop = new WP_Query( $args ); 

I then use a while loop to show each result on the page.

Is this even possible, and if so what am I doing wrong? Thanks

Answer 1

post_title isn't a valid argument to WP_Query. If you dump the SQL you will see that it is ignored:

string(189) "SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'investigator' AND (wp_posts.post_status = 'publish') ORDER BY wp_posts.post_title ASC LIMIT 0, 6"

You can use name (or pagename) instead, but you cannot push raw SQL through like that. It won't work:

string(158) "SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'like-%d00d' AND wp_posts.post_type = 'investigator' ORDER BY wp_posts.post_title ASC "

If you use the s argument-- like this 's' => $_POST['s']--, you get something like you are looking for:

string(310) "SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND (((wp_posts.post_title LIKE '%d00d%') OR (wp_posts.post_content LIKE '%d00d%'))) AND (wp_posts.post_password = '') AND wp_posts.post_type = 'investigator' AND (wp_posts.post_status = 'publish') ORDER BY wp_posts.post_title ASC LIMIT 0, 6"

But you are searching more fields than just the title. To restrict that to the title only, you can use a filter from another of my answers:

function only_title_search_wpse_119422( $search ) {
    remove_filter( 'posts_search', 'only_title_search_wpse_119422' );

    global $wpdb;

    $pattern = "/\({$wpdb->posts}.post_title[^)]+\)/";
    preg_match_all( $pattern, $search, $matches );

    if ( ! empty( $matches[0] ) ) {
        $search = sprintf(
            " AND (%s)",
            implode( " AND ", $matches[0] )
        );
    }

    return $search;
}
add_filter( 'posts_search', 'only_title_search_wpse_119422' );