Search in Custom Fields

functions.php

/*////////////////////////////////////////////////
 //
 //	Search in custom fields
 //
 ////////////////////////////////////////////////*/

function cf_search_join( $join ) {
    global $wpdb;

    if ( is_search() ) {    
        $join .=' LEFT JOIN '.$wpdb->postmeta. ' cfmeta ON '. $wpdb->posts . '.ID = cfmeta.post_id ';
    }

    return $join;
}
add_filter('posts_join', 'cf_search_join' );

function cf_search_where( $where ) {
    global $pagenow, $wpdb;

    if ( is_search() ) {
        $where = preg_replace(
            "/\(\s*".$wpdb->posts.".post_title\s+LIKE\s*(\'[^\']+\')\s*\)/",
            "(".$wpdb->posts.".post_title LIKE $1) OR (cfmeta.meta_value LIKE $1)", $where );
    }

    return $where;
}

function cf_search_distinct( $where ) {
    global $wpdb;

    if ( is_search() ) {
        return "DISTINCT";
    }

    return $where;
}
add_filter('posts_join', 'cf_search_join' );
add_filter( 'posts_where', 'cf_search_where' );
add_filter( 'posts_distinct', 'cf_search_distinct' );